-adaptive-blur radius[xsigma]
Adaptively blur pixels, with decreasing effect near edges. A Gaussian
operator of the given radius and standard deviation (sigma) is used. If
sigma is not given it defaults to 1.
-adaptive-resize geometry
Resize the image using data-dependent triangulation. See Image Geometry for
complete details about the geometry argument. The -adaptive-resize option
defaults to data-dependent triangulation. Use the -filter to choose a
different resampling algorithm. Offsets, if present in the geometry string,
are ignored, and the -gravity option has no effect.
-adaptive-sharpen radius[xsigma]
Adaptively sharpen pixels, with increasing effect near edges. A Gaussian
operator of the given radius and standard deviation (sigma) is used. If
sigma is not given it defaults to 1.
-adjoin
Join images into a single multi-image file. This option is enabled by
default. An attempt is made to save all images of an image sequence into the
given output file. However, some formats, such as JPEG and PNG, do not
support more than one image per file, and in that case ImageMagick is forced
to write each image as a separate file. As such, if more than one image
needs to be written, the filename given is modified by adding a -scene
number before the suffix, in order to make distinct names for each image.
Use +adjoin to force each image to be written to separate files, whether or
not the file format allows multiple images per file (for example, GIF, MIFF,
and TIFF).
Including a C-style integer format string in the output filename will
automagically enable +adjoin and are used to specify where the -scene number
is placed in the filenames. These strings, such as '%d' or '%03d', are
familiar to those who have used the standard printf()' C-library function.
As an example, the command
$magick> convert logo: rose: -morph 15 my%02dmorph.jpg
will create a sequence of 17 images named my00morph.jpg, my01morph.jpg,
my02morph.jpg, ..., my16morph.jpg.
In summary, ImageMagick tries to write all images to one file, but will use
multiple files if either (1) the output image's file format does not allow
multi-image files, (2) the +adjoin option is given, or (3) a C-style integer
format string is present in the output filename.
-affine sx,rx,ry,sy,tx,ty -affine sx,rx,ry,sy
Set the drawing transformation matrix for combined rotating and scaling.
This option sets a transformation matrix, encoded as (sx, rx, ry, sy, tx,
ty), for use by subsequent -draw or -transform options.
The matrix entries are entered as comma-separated numeric values with no
spaces.
Internally, the transformation matrix has 3x3 elements, but three of them
are omitted from the input because they are constant. The new (transformed)
coordinates (x', y') of a pixel at position (x, y) in the original image are
calculated using the following matrix equation.
The size of the resulting image is that of the smallest rectangle that
contains the transformed source image. The parameters tx and ty subsequently
shift the image pixels so that those that are moved out of the image area
are cut off.
The transformation matrix complies with the left-handed pixel coordinate
system: positive x and y directions are rightward and downward, resp.;
positive rotation is clockwise.
If the translation coefficients tx and ty are omotted they default to 0,0.
Therefore, four parameters suffice for rotation and scaling without
translation.
Scaling by the factors sx and sy in the x and y directions, respectively, is
accomplished with the following.
-affine sx,0,0,sy
Translation by a displacement (tx, ty) is accomplished like so:
-affine 1,0,0,1,tx,ty
Rotate clockwise about the origin (the upper left-hand corner) by an angle a
by letting c = cos(a), s = sin(a), and using the following.
-affine c,s,-s,c
The cumulative effect of a sequence of -affine transformations can be
accomplished by instead by a single -affine operation using the matrix equal
to the product of the matrices of the individual transformations.
An attempt is made to detect near-singular transformation matrices. If the
matrix determinant has a sufficiently small absolute value it is rejected.
-alpha type
Gives control of the alpha/matte channel of an image. Used to set a flag on
an image indicating whether or not to use existing alpha channel data, to
create an alpha channel, or to perform other operations on the alpha
channel. Choose the argument type from the list below.
type Description Off or Deactivate Disables the image's transparency
channel. Does not delete or change the existing data, just turns off the use
of that data. This is the same as the older +matte operator. On or
Activate Enables the image's use of transparency. If transparency data
does not already exist, allocates the data and sets it to opaque. If the
image has transparency data, the channel is enabled and the transparency
data is not changed or modified in any way. This is NOT the same as the
older -matte operator. Set Turns 'On' the alpha/matte channel and if it
was previously turned off resets the channel to opaque. If the image already
had the alpha channel turned on, it will have no effect. This is the same as
the older -matte operator. Opaque Turns 'On' the alpha/matte channel and
forces it to be fully opaque. Transparent Turns 'On' the alpha/matte
channel and forces it to be fully transparent. This effectively creates a
fully transparent image the same size as the original and with all its
original RGB data still intact. Extract Copies the alpha channel values
into all the color channels and turns 'Off' the the image's transparency, so
as to generate a gray-scale mask of the image's shape. This is the inverse
of 'Copy'. Copy Turns 'On' the alpha/matte channel, then copies the
gray-scale intensity of the image, as an alpha mask, into the alpha channel,
converting a gray-scale mask into a transparent shaped image ready to be
colored appropriately. The color channels are not modified. Shape As per
'Copy' but also colors the resulting shape mask with the current background
color. Background Set any fully-transparent pixel to the background
color. Note that while the +matte operation is the same as "-alpha off", the
-matte operation is the same as "-alpha set" and not "-alpha on". That is,
"-alpha set" will ensure that the written image is opaque if the original
image had no transparency channel enabled, regardless if transparency data
is already present.
-annotate degrees text -annotate XdegreesxYdegrees text -annotate
XdegreesxYdegrees {+-}tx{+-}ty text
Annotate an image with text. This is a convenience for annotating an image
with text. For more precise control over text annotations, use -draw.
The values Xdegrees and Ydegrees control the shears with respect to the ,
respectively, applied to the text, while tx and ty are offsets that give the
location of the text relative to the upper left corner of the image.
Using -annotate degrees or -annotate degreesxdegrees produces an unsheared
rotation of the text. The direction of the rotation is positive, which means
a clockwise rotation if degrees is positive. (This conforms to the usual
mathematical convention once it is realized that the positive y–direction is
conventionally considered to be downward for images.)
The new (transformed) coordinates (x', y') of a pixel at position (x, y) in
the image are calculated using the following matrix equation.
If tx and ty are omitted, they default to 0. This makes the bottom-left of
the text becomes the upper-left corner of the image, which is probably
undesirable. Adding a -gravity option in this case leads to nice results.
Text is any UTF-8 encoded character sequence. If text is of the form
'@mytext.txt', the text is read from the file mytext.txt. Text in a file is
taken literally; no embedded formatting characters are recognized.
-antialias
Enable/Disable of the rendering of anti-aliasing pixels when drawing fonts
and lines. By default, objects (e.g. text, lines, polygons, etc.) are
antialiased when drawn. Use +antialias to disable the addition of
antialiasing edge pixels. This will then reduce the number of colors added
to an image to just the colors being directly drawn. That is, no mixed
colors will be added when drawing such objects.
-append
Join current images vertically or horizontally. This option creates a single
longer image image, by joining all the current images in sequence
top-to-bottom. Use +append to stack images left-to-right.
If they are not of the same width, narrower images are padded with the
current -background color setting, and their position relative to each other
can be controled by the current -gravity setting.
-attenuate value
Lessen (or intensify) when adding noise to an image. -authenticate password
Decrypt a PDF with a password. Use this option to supply a password for
decrypting a PDF that has been encrypted using Microsoft Crypto API (MSC
API). The encrypting using the MSC API is not supported.
For a different encryption method, see -encipher and -decipher.
-auto-gamma
Automagically adjust gamma level of image. This calculates the mean values
of an image, then applies a calculated -gamma adjustment so that is the mean
color exists in the image it will get a have a value of 50%.
This means that any solid 'gray' image will become 50% gray.
This works well for real-life images with little or no extreme dark and
light areas, but tend to fail for images with large amounts of bright sky or
dark shadows. It also does not work well for diagrmas or cartoon like
images.
It uses the -channel setting, (including the 'sync' flag for channel
syncronization), to determine which color values will be used and modified.
As the default -channel setting is 'RGB,sync', channels will be modified
together by the same gamma value, preserving colors.
-auto-level
Automagically adjust color levels of image. This is a 'perfect' image
normalization operator. It finds the exact mimimum and maximum color values
in the image and then applies a -level operator to stretch the values to the
full range of values.
The operator is not typically used for real-life images, image scans, or
JPEG format images, as a single 'out-rider' pixel can set a bad min/max
values for the -level operation. On the other hand it is the right operator
to use for color stretching gradient images being used to generate Color
lookup tables, distortion maps, or other 'mathematically' defined images.
The operator is very similar to the -normalize, -contrast-stretch, and
-linear-stretch operators, but without 'histogram binning' or 'clipping'
problems that these operators may have. That is -auto-level is the perfect
or ideal version these operators.
It uses the -channel setting, (including the special 'sync' flag for channel
syncronization), to determine which color values will be used and modified.
As the default +channel setting is 'RGB,sync', the 'sync' will ensure that
the color channels will be modified together by the same gamma value,
preserving colors, and ignoring transparency.
-auto-orient
Automagically orient (rotate) an image created by a digital camera. This
operator reads and resets the EXIF image profile setting 'Orientation' and
then performs the appropriate 90 degree rotation on the image to orient the
image, for correct viewing.
This EXIF profile setting is usually set using a gravity sensor in digital
camara, however photos taken directly downward or upward may not have an
appropriate value. Also images that have been orientation 'corrected'
without reseting this setting, may be 'corrected' again resulting in a
incorrect result. If the he EXIF profile was previously stripped, the
-auto-orient operator will do nothing.
-average
Average a set of images. An error results if the images are not identically
sized.
-backdrop
Display the image centered on a backdrop. [animate, display] This
backdrop covers the entire workstation screen and is useful for hiding other
X window activity while viewing the image. The color of the backdrop is
specified as the background color. The color is specified using the format
described under the -fill option.
-background color
Set the background color. The color is specified using the format described
under the -fill option. The default background color (if none is specified
or found in the image) is white.
-bench iterations
Measure performance. Repeat the entire command for the given number of
iterations and report the user-time and elapsed time. For instance, consider
the following command and its output. Modify the benchmark with the
-duration to run the benchmark for a fixed number of seconds and -concurrent
to run the benchmark in parallel (requires the OpenMP feature).
$magick> convert logo: -resize 1000% -bench 5 logo.png Performance: 5i
0.875657ips 6.880u 0:05.710
In this example, 5 iterations were completed at 0.875657 iterations per
second, using 6.88 seconds of the user's allotted time, for a total elapsed
time of 5.71 seconds.
-bias value{%}
Add bias when convolving an image. This option shifts the output of
‑convolve so that positive and negative results are relative to the
specified bias value.
This is important for non-HDRI compilations of ImageMagick when dealing with
convolutions that contain negative as well as positive values. This is
especially the case with convolutions involving high pass filters or edge
detection. Without an output bias, the negative values are clipped at zero.
When using an ImageMagick with the HDRI compile-time setting, ‑bias is not
needed, as ImageMagick is able to store/handle any negative results without
clipping to the color value range (0..QuantumRange).
See the discussion on HDRI implementations of ImageMagick on the page High
Dynamic-Range Images. For more about HDRI go the ImageMagick Usage pages or
this Wikipedia entry.
-black-point-compensation
Use black point compensation. -black-threshold value{%}
Force to black all pixels below the threshold while leaving all pixels at or
above the threshold unchanged. The threshold value can be given as a
percentage or as an absolute integer value within [0, QuantumRange]
corresponding to the desired ‑channel value. See ‑threshold for more details
on thresholds and resulting values.
-blend percent
blend an image into another by the given percent. [composite] Blend will
average the images together ('plus') according to the percentages given and
each pixels transparency. If only a single percentage value is given it sets
the weight of the composite or 'source' image, while the background image is
weighted by the exact opposite amount. That is a -blend 30 merges 30% of the
'source' image with 70% of the 'destination' image. Thus it is equivalent to
-blend 30x70.
-blue-primary x,y
Set the blue chromaticity primary point. -blue-shift factor
simulate a scene at nighttime in the moonlight. Start with a factor of 1.5
-blur radius -blur radiusxsigma
Reduce image noise and reduce detail levels. Convolve the image with a
Gaussian or normal distribution. The formula is:
Where r is the blur radius (r2 = u2 + v2), and σ is the standard deviation
of the Gaussian distribution. As a guideline, set r to approximately 3σ. If
a radius of 0 is specified, ImageMagick selects a suitable radius for you.
This option differs from -gaussian-blur simply by taking advantage of the
separability properties of the distribution. Here we apply a
single-dimensional Gaussian matrix in the horizontal direction, then repeat
the process in the vertical direction.
The -virtual-pixel setting will determine how pixels which are outside the
image proper are blurred into the final result.
-blur Width[xHeight[+Angle]]
Variably blur and image according to the overlay mapping. [composite]
Each pixel in the overlaid region is replaced with an Elliptical Weighted
Average (EWA) of the source image, scaled according to the grayscale
mapping.
The ellipse is weighted with sigma set to the given Width and Height. The
Height defaults to the Width for a normal circular Guassian weighting. The
Angle will rotate the ellipse from horizontal clock-wise.
The -virtual-pixel setting will determine how pixels which are outside the
image proper are blurred into the final result.
-border geometry
Surround the image with a border of color. Set the width and height using
the size portion of the gravity argument. See Image Geometry for complete
details about the geometry argument. Offsets are ignored.
Set the border color by preceding with the -bordercolor setting.
See also the -frame option, which has more functionality.
-bordercolor color
Set the border color. The color is specified using the format described
under the -fill option.
The default border color is #DFDFDF, this shade of gray.
-borderwidth geometry
Set the border width. [animate, display] -brightness-contrast brightness
-brightness-contrast brightness{xcontrast}{%}}
Adjust the brightness and/or contrast of the image. Brightness and Contrast
values apply changes to the input image. They are not absolute settings. A
brightness or contrast value of zero means no change. The range of values is
-100 to +100 on each. Positive values increase the brightness or contrast
and negative values decrease the brightness or contrast. To control only
contrast, set the brightness=0. To control only brightness, set contrast=0
or just leave it off.
You may also use -channel to control which channels to apply the brightness
and/or contrast change. The default is to apply the same transformation to
all channels.
Brightness and Contrast arguments are converted to offset and slope of a
linear transform and applied using -function polynomial "slope,offset".
The slope varies from 0 at contrast=-100 to almost vertical at
contrast=+100. For brightness=0 and contrast=-100, the result will be
totally midgray. For brightness=0 and contrast=+100, the result will
approach but not quite reach a threshold at midgray; that is the linear
transformation will be a a very steep vertical line at mid gray.
Negative slopes, i.e. negating the image, are not possible with this
function. All achievable slopes will be zero or positive.
The offset varies from -0.5 at brightness=-100 to 0 at brightness=0 to +0.5
at brightness=+100. Thus, when contrast=0 and brightness=100, the result
will be totally white. Similarly, when contrast=0 and brightness=-100, the
result will be totally black.
As the range of values for the arguments are -100 to +100, adding the '%'
symbol will be no different than leaving it off.
-cache threshold
(This option has been replaced by the -limit option.) -caption string
Assign a caption to an image. -cdl filename
color correct with a color decision list. Here is an example color
correction collection:
0.9 1.2 0.5 0.4 -0.5 0.6 1.0 0.8 1.5
0.85
-channel type
Specify those image color channels to which subsequent operators are
limited. Choose from: Red, Green, Blue, Alpha, Cyan, Magenta, Yellow, Black,
Opacity, Index, RGB, RGBA, CMYK, or CMYKA.
To print a complete list of channel types, use -list channel.
The channels above can be specified as a comma-separated list or can be
abbreviated as a concatenation of the letters 'R', 'G', 'B', 'A', 'O', 'C',
'M', 'Y', 'K'. For example, to negate only the alpha channel of an image,
use
-channel Alpha -negate
Some operators also allow the use of a special channel flag 'sync'. If
present operators that understand this flag will apply the exact same image
modification to all the image channels in the image so as to ensure that
colors are kept 'in-sync'. Without this flag such operators will apply there
function to each channel separately. See -auto-level and -auto-gamma for
examples of such an operator. By default, ImageMagick sets -channel to the
value 'RGB,sync', which specifies that operators act on all channels except
the opacity channel, and that all the color channels are to be modified in
exactly the same way. The 'plus' form +channel will reset the value back to
this default.
Options that are affected by the -channel setting include the following.
-auto-gamma, -auto-level, -black-threshold, -blur, -clamp, -clut, -combine,
-contrast-stretch, -evaluate, -function, -fx, -gaussian-blur, -hald-clut,
-motion-blur, -negate, -normalize, -ordered-dither, -radial-blur,
-random-threshold, -separate, and -threshold, and -white-threshold.
Warning, some operators behave differentally when the +channel default
setting is in effect, verses ANY user defined -channel setting (including
the equivelent of the default). For example -threshold will by default
gray-scale the image before thresholding, if no -channel setting has been
defined.
Also some operators such as -blur, -gaussian-blur, will modify their
handling of the color channels if the 'alpha' channel is also enabled by
-channel. Generally this done to ensure that fully-transparent colors are
treated as being fully-transparent, and thus any underlying 'hidden' color
has no effect on the final results. Typically resulting in 'halo' effects.
As a alpha channel is optional within images some operators will read the
color channels of an image as a greyscale alpha mask, when the image has no
alpha channel present, but the -channel setting tells the operator to apply
the alpha channel. The -clut operator is a good example of this.
-clamp
Restrict image colors from 0 to the quantum depth. -charcoal factor
Simulate a charcoal drawing. -chop geometry
Remove pixels from the interior of an image. See Image Geometry for complete
details about the geometry argument. The width and height given in the of
the size portion of the geometry argument give the number of columns and
rows to remove. The offset portion of the geometry argument is influenced by
a -gravity setting, if present.
The -chop option removes entire rows and columns, and moves the remaining
corner blocks leftward and upward to close the gaps.
-clip
Apply the clipping path if one is present. If a clipping path is present, it
is applied to subsequent operations.
For example, in the command
$magick> convert -clip -negate cockatoo.tif negated.tif
only the pixels within the clipping path are negated.
The -clip feature requires the XML library. If the XML library is not
present, the option is ignored.
-clip-mask
Clip the image as defined by this mask. -clip-path id
Clip along a named path from the 8BImageMagick profile. -clone index(s)
Make a copy of an image (or images). Specify the image by its index in the
sequence. The first image is index 0. Negative indexes are relative to the
end of the sequence; for example, −1 represents the last image of the
sequence. Specify a range of images with a dash (e.g. 0−4). Separate
multiple indexes with commas but no spaces (e.g. 0,2,5). Use +clone make a
copy of the last image in the image sequence.
-clut
Replace the channel values in the first image using each corresponding
channel in the second image as a color lookup table. The second (LUT) image
is ordinarily a gradient image containing the histogram mapping of how each
channel should be modified. Typically it is a either a single row or column
image of replacement color values. If larger than a single row or column,
values are taken from a diagonal line from top-left to bottom-right corners.
The lookup is further controlled by the -interpolate setting, which is
especially handy for an LUT which is not the full length needed by the
ImageMagick installed Quality (Q) level. Good settings for this are the
'bilinear' and 'bicubic' interpolation settings, which give smooth color
gradients, and the 'integer' setting for a direct, unsmoothed lookup of
color values.
This operator is especially suited to replacing a grayscale image with a
specific color gradient from the CLUT image.
Only the channel values defined by the -channel setting will have their
values replaced. In particular, since the default -channel setting is RGB,
this means that transparency (alpha/matte channel) is not affected, unless
the -channel setting is modified. When the alpha channel is set, it is
treated by the -clut operator in the same way as the other channels,
implying that alpha/matte values are replaced using the alpha/matte values
of the original image.
If either the image being modified, or the lookup image, conatins no
transparency (i.e. -alpha is turned 'off') but the -channel setting includes
alpha replacement, then it is assumed that image represents a gray-scale
graident which will be used for the replacement alpha values. That is you
can use a gray-scale CLUT image to adjust a existing images alpha channel,
or you can color a gray-scale image using colors form CLUT containing the
desired colors, including transparency.
See also -hald-clut which replaces colors according the lookup of the full
color RGB value from a 2D representation of a 3D color cube.
-coalesce
Fully define the look of each frame of an GIF animation sequence, to form a
'film strip' animation. Overlay each image in an image sequence according to
its -dispose meta-data, to reproduce the look of an animation at each point
in the animation sequence. All images should be the same size, and are
assigned appropriate GIF disposal settings for the animation to continue
working as expected as a GIF animation. Such frames are more easilly viewed
and processed than the highly optimized GIF overlay images.
The animation can be re-optimized after processing using the -layers method
'optimize', though there is no guarantee that the restored GIF animation
optimization is better than the original.
-colorize value
Colorize the image by an amount specified by value using the color specified
by the most recent -fill setting. Specify the amount of colorization as a
percentage. Separate colorization values can be applied to the red, green,
and blue channels of the image with a comma-delimited list of colorization
values (e.g., -colorize 0,0,50).
-colormap type
Define the colormap type. [animate, display] The type can be shared or
private.
This option only applies when the default X server visual is PseudoColor or
GrayScale. Refer to -visual for more details. By default, a shared colormap
is allocated. The image shares colors with other X clients. Some image
colors could be approximated, therefore your image may look very different
than intended. If private is chosen, the image colors appear exactly as they
are defined. However, other clients may go technicolor when the image
colormap is installed.
-colors value
Set the preferred number of colors in the image. The actual number of colors
in the image may be less than your request, but never more. Note that this a
color reduction option. Images with fewer unique colors than specified by
value will have any duplicate or unused colors removed. The ordering of an
existing color palette may be altered. When converting an image from color
to grayscale, it is more efficient to convert the image to the gray
colorspace before reducing the number of colors. Refer to the color
reduction algorithm for more details.
-colorspace value
Set the image colorspace. Choices are:
CMY CMYK Gray HSB HSL HWB Lab Log OHTA Rec601Luma Rec601YCbCr Rec709Luma
Rec709YCbCr RGB sRGB Transparent XYZ YCbCr YCC YIQ YPbPr YUV To print a
complete list of colorspaces, use -list colorspace.
For a more accurate color conversion to or from the RGB, CMYK, or grayscale
colorspaces, use the -profile option.
Conversion Of RGB To Other Color Spaces CMY C=QuantumRange−R
M=QuantumRange−G Y=QuantumRange−B CMYK — starts with CMY from above
K=min(C,Y,M) C=QuantumRange*(C−K)/(QuantumRange−K)
M=QuantumRange*(M−K)/(QuantumRange−K) Y=QuantumRange*(Y−K)/(QuantumRange−K)
Gray Gray = 0.29900*R+0.58700*G+0.11400*B HSB — Hue, Saturation, Brightness;
like a cone peak downward H=angle around perimeter (0 to 360 deg); H=0 is
red; increasing angles toward green S=distance from axis outward B=distance
along axis from bottom upward; B=max(R,G,B); intensity-like HSL — Hue,
Saturation, Lightness; like a double cone end-to-end with peaks at very top
and bottom H=angle around perimeter (0 to 360 deg); H=0 is red; increasing
angles toward green S=distance from axis outward L=distance along axis from
bottom upward; L=0.5*max(R,G,B) + 0.5*min(R,G,B); intensity-like HWB — Hue,
Whiteness, Blackness Hue (complicated equation) Whiteness (complicated
equation) Blackness (complicated equation) LAB L (complicated equation
relating X,Y,Z) A (complicated equation relating X,Y,Z) B (complicated
equation relating X,Y,Z) LOG I1 (complicated equation involving logarithm of
R) I2 (complicated equation involving logarithm of G) I3 (complicated
equation involving logarithm of B) OHTA — approximates principal components
transformation I1=0.33333*R+0.33334*G+0.33333*B; intensity-like
I2=(0.50000*R+0.00000*G−0.50000*B)*(QuantumRange+1)/2
I3=(−0.25000*R+0.50000*G−0.25000*B)*(QuantumRange+1)/2 Rec601Luma Gray =
0.29900*R+0.58700*G+0.11400*B Rec601YCbCr
Y=0.299000*R+0.587000*G+0.114000*B; intensity-like
Cb=(−0.168736*R-0.331264*G+0.500000*B)*(QuantumRange+1)/2
Cr=(0.500000*R−0.418688*G−0.081312*B)*(QuantumRange+1)/2 Rec709Luma
Gray=0.21260*R+0.71520*G+0.07220*B Rec709YCbCr
Y=0.212600*R+0.715200*G+0.072200*B; intensity-like
Cb=(−0.114572*R−0.385428*G+0.500000*B)*(QuantumRange+1)/2
Cr=(0.500000*R−0.454153*G−0.045847*B)*(QuantumRange+1)/2 sRGB if Rs ≤ .03928
then Rs=R/12.92 else Rs=((R+.055)/1.055)^2.4 if Gs ≤ .03928 then Gs=B/12.92
else Gs=((G+.055)/1.055)^2.4 if Bs ≤ .03928 then Bs=B/12.92 else
Bs=((B+.055)/1.055)^2.4 XYZ X=0.4124240*R+0.3575790*G+0.1804640*B
Y=0.2126560*R+0.7151580*G+0.0721856*B Z=0.0193324*R+0.1191930*G+0.9504440*B
YCC Y=(0.29900*R+0.58700*G+0.11400*B) (with complicated scaling);
intensity-like C1=(−0.29900*R−0.58700*G+0.88600*B) (with complicated
scaling) C2=(0.70100*R−0.58700*G−0.11400*B) (with complicated scaling) YCbCr
Y=0.299000*R+0.587000*G+0.114000*B; intensity-like
Cb=(−0.168736*R−0.331264*G+0.500000*B)*(QuantumRange+1)/2
Cr=(0.500000*R−0.418688*G−0.081312*B)*(QuantumRange+1)/2 YIQ
Y=0.29900*R+0.58700*G+0.11400*B; intensity-like
I=(0.59600*R−0.27400*G−0.32200*B)*(QuantumRange+1)/2
Q=(0.21100*R−0.52300*G+0.31200*B)*(QuantumRange+1)/2 YPbPr
Y=0.299000*R+0.587000*G+0.114000*B; intensity-like
Pb=(−0.168736*R−0.331264*G+0.500000*B)*(QuantumRange+1)/2
Pr=(0.500000*R−0.418688*G−0.081312*B)*(QuantumRange+1)/2 YUV
Y=0.29900*R+0.58700*G+0.11400*B; intensity-like
U=(−0.14740*R−0.28950*G+0.43690*B)*(QuantumRange+1)/2
V=(0.61500*R−0.51500*G−0.10000*B)*(QuantumRange+1)/2 -combine
Combine one or more images into a single image. The channels (previously set
by -channel) of the combined image are taken from the grayscale values of
each image in the sequence, in order. For the default -channel setting of
RGB, this means the first image is assigned to the Red channel, the second
to the Green channel, the third to the Blue.
This option can be thought of as the inverse to -separate, so long as the
channel settings are the same. Thus, in the following example, the final
image should be a copy of the original.
$magick> convert original.png -channel RGB -separate sepimage.png $magick>
convert sepimage-0.png sepimage-1.png sepimage-2.png -channel RGB -combine
imagecopy.png
-comment string
Embed a comment in an image. This option places comments in a non-pixel
portion of the image file. For a comment to be visibly written on the image
itself, use the -annotate or -draw options.
Use this option to assign a specific comment to the image, when writing to
an image format that supports comments. You can include the image filename,
type, width, height, or other image attribute by embedding special format
characters listed under the -format option. The comment is not drawn on the
image, but is embedded in the image datastream via "Comment" tag or similar
mechanism.
For example,
-comment "%m:%f %wx%h"
produces an image comment of MIFF:bird.miff 512x480 for an image titled
bird.miff and whose width is 512 and height is 480.
If the first character of string is @, the image comment is read from a file
titled by the remaining characters in the string. Comments in a file are
literal; no embedded formatting characters are recognized.
-compose operator
Set the type of image composition. The description of composition uses
abstract terminology in order to allow the description to be more precise,
while avoiding constant values which are specific to a particular build
configuration. Each image pixel is represented by red, green, and blue
levels (which are equal for a gray pixel). The build-dependent value
QuantumRange is the maximum integral value which may be stored, per pixel,
in the red, green, or blue channels of the image. Each image pixel may also
optionally (if the image matte channel is enabled) have an associated level
of opacity, ranging from opaque to transparent, which may be used to
determine the influence of the pixel color when compositing the pixel with
another image pixel. If the image matte channel is disabled, then all pixels
in the image are treated as opaque. The color of an opaque pixel is fully
visible while the color of a transparent pixel color is entirely absent
(pixel color is ignored).
By definition, raster images have a rectangular shape. All image rows are of
equal length, as are all image columns. By treating the alpha channel as a
visual "mask" the rectangular image may be given a "shape" by treating the
alpha channel as a cookie-cutter for the image. This is done by setting the
pixels within the shape to be opaque, with pixels outside the shape set as
transparent. Pixels on the boundary of the shape may be between opaque and
transparent in order to provide antialiasing (visually smooth edges). The
description of the composition operators use this concept of image "shape"
in order to make the description of the operators easier to understand.
While it is convenient to describe the operators in terms of "shapes" they
are by no means limited to mask-style operations since they are based on
continuous floating-point mathematics rather than simple boolean operations.
The following alpha blending (Duff-Porter) compose methods are available:
Method Description clear Both the color and the alpha of the
destination are cleared. Neither the source nor the destination are used
(except for destinations size and other meta-data which is always preserved.
src The source is copied to the destination. The destination is not used
as input, though it is cleared. dst The destination is left untouched.
The source image is completely ignored. src-over The source is composited
over the destination. this is the default alpha blending compose method,
when neither the compose setting is set, nor is set in the image meta-data.
dst-over The destination is composited over the source and the result
replaces the destination. src-in The part of the source lying inside of
the destination replaces the destination. dst-in The part of the
destination lying inside of the source replaces the destination. Areas not
overlaid are cleared. src-out The part of the source lying outside of the
destination replaces the destination. dst-out The part of the destination
lying outside of the source replaces the destination. src-atop The part
of the source lying inside of the destination is composited onto the
destination. dst-atop The part of the destination lying inside of the
source is composited over the source and replaces the destination. Areas not
overlaid are cleared. xor The part of the source that lies outside of the
destination is combined with the part of the destination that lies outside
of the source. Source or Destination, but not both. Any of the 'Src-*'
methods can also be specified without the 'Src-' part. For example the
defaul compose method can be specified as just 'Over'.
The following mathemathical composition methods are also available.
Typically these use the default 'Over' alpha blending when transparencies
are also involved, except for 'Plus', 'Minus', 'Add', and 'Subtract', which
also composes the alpha channel using the same process as the color
channels. This allows them to be used for special image masking techniques.
Method Description multiply The source is multiplied by the
destination and replaces the destination. The resultant color is always at
least as dark as either of the two constituent colors. Multiplying any color
with black produces black. Multiplying any color with white leaves the
original color unchanged. screen The source and destination are
complemented and then multiplied and then replace the destination. The
resultant color is always at least as light as either of the two constituent
colors. Screening any color with white produces white. Screening any color
with black leaves the original color unchanged. plus The source is added
to the destination and replaces the destination. This operator is useful for
averaging or a controled merger of two images, rather than a direct overlay.
add As per 'plus' but transparency data is treated as matte values. As
such any transparent areas in either image remain transparent.
minus Subtract the colors in the source image from the destination image.
When transparency is involved, opaque areas is subtracted from any
destination opaque areas. subtract Subtract the colors in the source
image from the destination image. When transparency is involved transparent
areas are subtracted, so only the opaque areas in the source remain opaque
in the destination image. difference Subtracts the darker of the two
constituent colors from the lighter. Painting with white inverts the
destination color. Painting with black produces no change.
exclusion Produces an effect similar to that of 'difference', but appears
as lower contrast. Painting with white inverts the destination color.
Painting with black produces no change. darken Selects the darker of the
destination and source colors. The destination is replaced with the source
when the source is darker, otherwise it is left unchanged.
lighten Selects the lighter of the destination and source colors. The
destination is replaced with the source when the source is lighter,
otherwise it is left unchanged. linear-dodge This is equivelent to 'Plus'
in that the color channels are simply added, however it does not 'Plus' the
alpha channel, but uses the normal 'Over' alpha blending, which
transparencies are involved. Produces a sort of additive multiply-like
result. Added ImageMagick version 6.5.4-3. linear-burn As 'Linear-Dodge',
but also subtract one from the result. Sort of a additive 'Screen' of the
images. Added ImageMagick version 6.5.4-3. color-dodge Brightens the
destination color to reflect the source color. Painting with black produces
no change. color-burn Darkens the destination color to reflect the source
color. Painting with white produces no change. Fixed in ImageMagick version
6.5.4-3. overlay Multiplies or screens the colors, dependent on the
destination color. Source colors overlay the destination whilst preserving
its highlights and shadows. The destination color is not replaced, but is
mixed with the source color to reflect the lightness or darkness of the
destination. hard-light Multiplies or screens the colors, dependent on
the source color value. If the source color is lighter than 0.5, the
destination is lightened as if it were screened. If the source color is
darker than 0.5, the destination is darkened, as if it were multiplied. The
degree of lightening or darkening is proportional to the difference between
the source color and 0.5. If it is equal to 0.5 the destination is
unchanged. Painting with pure black or white produces black or white.
linear-light Like 'Hard-Light' but using linear-dodge and linear-burn
instead. Increases contrast slightly with an impact on the foreground's
tonal values. soft-light Darkens or lightens the colors, dependent on the
source color value. If the source color is lighter than 0.5, the destination
is lightened. If the source color is darker than 0.5, the destination is
darkened, as if it were burned in. The degree of darkening or lightening is
proportional to the difference between the source color and 0.5. If it is
equal to 0.5, the destination is unchanged. Painting with pure black or
white produces a distinctly darker or lighter area, but does not result in
pure black or white. Fixed in ImageMagick version 6.5.4-3.
pegtop-light Almost equivelent to 'Soft-Light', but using a continuious
mathematical formula rather than two conditionally selected formulae. Added
ImageMagick version 6.5.4-3. vivid-light A modified 'Linear-Light'
designed to preserve very stong primary and secondary colors in the image.
Added ImageMagick version 6.5.4-3. pin-light Similar to 'Hard-Light', but
using sharp linear shadings, to similate the effects of a strong 'pinhole'
light source. Added ImageMagick version 6.5.4-3. Also included are these
special purpose compose methods:
Method Description copy-* Copy the specified channel (Red, Green,
Blue, Cyan, Magenta, Yellow, Black, or Opacity) in the source image to the
same channel in the destination image. If the channel specified does not
exist in the source image, (which can only happen for methods,
'copy-opacity' or 'copy-black') then it is assumed that the source image is
a special grayscale channel image of the values to be copied.
change-mask Replace any destination pixel that is the similar to the
source images pixel (as defined by the current -fuzz factor), with
transparency. On top of these composed methods are a few special ones that
not only require the two images that are being merged or overlaid, but have
some extra numerical arguments, which are tabled below.
In the "composite" command these composition methods are selected using
special options with the arguments needed. They are usually, but not always,
the same name as the composte 'method' they use, and replaces the normal use
of the -compose setting in the "composite" command. For example...
$magick> composite ... -blend 50x50 ...
As of IM v6.5.3-4 the "convert" command can now also supply these extra
arguments to its -composite operator, using the special -set attribute of
'option:compose:args'. This means you can now make use of these special
argumented -compose methods, those the argument and the method both need to
be set separatally. For example...
$magick> convert ... -compose blend -set option:compose:args 50x50
-composite ...
The following is a table of these special 'argumented' compose methods, with
a brief summary of what they do. For more details see the equivalent
"composite" command option name.
Method Description dissolve Arguments: src_percent[xdst_percent]
Equivalent to "composite" -dissolve Dissolve the 'source' image by the
percentage given before overlaying 'over' the 'destination' image. If
src_percent is greater than 100, it starts dissolving the main image so it
will become transparent at a value of '200'. If both percentages are given,
each image are dissolved to the percentages given. blend Arguments:
src_percent[xdst_percent] Equivalent to "composite" -blend Average the
images together ('plus') according to the percentages given and each pixels
transparency. If only a single percentage value is given it sets the weight
of the composite or 'source' image, while the background image is weighted
by the exact opposite amount. That is a -blend 30 merges 30% of the 'source'
image with 70% of the 'destination' image. Thus it is equivalent to -blend
30x70. mathematics Arguments: A, B, C, D Not available in "composite" at
this time. Merge the source and destination images according to the formula
A*Sc*Dc + B*Sc + C*Dc + D Can be used to generate a custom composition
method that would otherwise need to be implemented using the slow -fx DIY
image operator. Added to ImageMagick version 6.5.4-3. modulate Arguments:
brightness[xsaturation] Equivalent to "composite" -watermark Take a
grayscale image (with alpha mask) and modify the destination image's
brightness according to watermark image's grayscale value and the brightness
percentage. The destinations color saturation attribute is just direct
modified by the saturation percentage, which defaults to 100 percent (no
color change). displace Arguments: X-scale[xY-scale][!][%] Equivalent to
"composite" -displace With this option, the 'overlay' image, and optionally
the 'mask' image, is used as a relative displacement map, which is used to
displace the lookup of what part of the destination image is seen at each
point of the overlaid area. Much like the displacement map is a 'lens' that
distorts the original 'background' image behind it.
The X-scale is modilated by the 'red' channel of the overlay image while the
Y-scale is modulated by the green channel, (the mask image if given is
rolled into green channel of the overlay image. This separation allows you
to modulate the X and Y lookup displacement separatally allowing you to di 2
dimentional displacements, rather than 1 dimentional verctored displacements
(using grayscale image).
If the overlay image contains transparency this is used as a mask of the
resulting image to remove 'invalid' pixels.
The '%' flag makes the displacement scale relative to the size of the
overlay image (100% = half width/height of image). Using '!' switches
percentage arguments to refer to the destination image size instead.
Special flags were added Added to ImageMagick version 6.5.3-5.
distort Arguments: X-scale[xY-scale[+X-center+Y-center]][!][%] Not
available in "composite" at this time. Exactly as per 'Displace' (above),
but using absolute coordinates, relative to the center of the overlay (or
that given). Basically allows you to generate absolute distortion maps where
'black' will look up the left/top edge, and 'white' looks up the
bottom/right edge of the destination image, according to the scale given.
The '!' flag not only switches percentage scaling, to use the destination
image, but also the image the center offset of the lookup. This means the
overlay can lookup a completely different region of the destination image.
Added to ImageMagick version 6.5.3-5. blur Arguments:
Width[xHeight[+Angle]] Equivalent to "composite" -blur A Variable Blur
Mapping Composition method, where each pixel in the overlaid region is
replaced with an Elliptical Weighted Average (EWA), with an ellipse
(typically a circle) of the given sigma size, scaled according to overlay
(source image) grayscale mapping.
As per 'Displace' and 'Distort', the red channel will modulate the width of
the ellipse, while the green channel will modulate the height of the
ellipse. However at this time the ellipse angle is not modulated though this
may be a future posibility (perhaps with a special flag to enable use of
blur channel for this purpose).
Added to ImageMagick version 6.5.4-0. To print a complete list of all the
available compose operators, use -list compose.
-composite
Perform alpha composition on the current image sequence. Take the first
image 'destination' and overlay the second 'source' image according to the
current -compose setting. The location of the 'source' or 'overlay' image is
controlled according to -geometry, and -geometry settings.
If a third image is given this is treated as a gray-scale 'mask' image
relative to the first 'destination' image. This mask will limit what parts
of the destination can be modified by the image composition. However for the
'displace' compose method, the mask is used to provide a separate
Y-displacement image instead.
If a -compose method requires extra numerical arguments or flags these can
be provided by setting the -set 'option:compose:args' appropriatally for the
compose method.
Some -compose methods can modify the 'destination' image outside the overlay
area. You can disable this by setting the special -set
'option:compose:outside-overlay' to 'false'.
-compress type
Use pixel compression specified by type when writing the image. Choices are:
None, BZip, Fax, Group4, JPEG, JPEG2000, Lossless, LZW, RLE or Zip.
To print a complete list of compression types, use -list compress.
Specify +compress to store the binary image in an uncompressed format. The
default is the compression type of the specified image file.
If LZW compression is specified but LZW compression has not been enabled,
the image data is written in an uncompressed LZW format that can be read by
LZW decoders. This may result in larger-than-expected GIF files.
Lossless refers to lossless JPEG, which is only available if the JPEG
library has been patched to support it. Use of lossless JPEG is generally
not recommended.
Use the -quality option to set the compression level to be used by JPEG,
PNG, MIFF, and MPEG encoders. Use the -sampling-factor option to set the
sampling factor to be used by JPEG, MPEG, and YUV encoders for down-sampling
the chroma channels.
-contrast
Enhance or reduce the image contrast. This option enhances the intensity
differences between the lighter and darker elements of the image. Use
-contrast to enhance the image or +contrast to reduce the image contrast.
For a more pronounced effect you can repeat the option:
$magick> convert rose: -contrast -contrast rose_c2.png
-contrast-stretch black-point -contrast-stretch
black-point{xwhite-point}{%}}
Increase the contrast in an image by stretching the range of intensity
values. While performing the stretch, black-out at most black-point pixels
and white-out at most white-point pixels. Or, if percent is used, black-out
at most black-point % pixels and white-out at most white-point % pixels.
Prior to ImageMagick 6.4.7-0, -contrast-stretch will black-out at most
black-point pixels and white-out at most total pixels minus white-point
pixels. Or, if percent is used, black-out at most black-point % pixels and
white-out at most 100% minus white-point % pixels.
Note that -contrast-stretch 0 will modify the image such that the image's
min and max values are stretched to 0 and QuantumRange, respectively,
without any loss of data due to burn-out or clipping at either end. This is
not the same as -normalize, which is equivalent to -contrast-stretch 2%x1%
(or prior to ImageMagick 6.4.7-0, -contrast-stretch 2%x99%).
Internally operator works by creating a histogram bin, and then uses that
bin to modify the image. As such some colors may be merged together when
they originally fell into the same 'bin'.
All the channels are normalized in concert by the came amount so as to
preserve color integrity, when the default +channel setting is in use.
Specifing any other -channel setting will normalize the RGB channels
independently.
See also -auto-level for a 'perfect' normalization of mathematical images.
This operator is under review for re-development.
-convolve kernel
Convolve an image with a user-supplied convolution kernel. The kernel is a
matrix specified as a comma-separated list of integers (with no spaces),
ordered left-to right, starting with the top row. Presently, only
odd-dimensioned kernels are supported, and therefore the number of entries
in the specified kernel must be 32=9, 52=25, 72=49, etc.
Note that the ‑convolve operator supports the ‑bias setting. This option
shifts the convolution so that positive and negative results are relative to
a user-specified bias value. This is important for non-HDRI compilations of
ImageMagick when dealing with convolutions that contain negative as well as
positive values. This is especially the case with convolutions involving
high pass filters or edge detection. Without an output bias, the negative
values is clipped at zero.
When using an ImageMagick with the HDRI compile-time setting, ‑bias is not
needed, as ImageMagick is able to store/handle any negative results without
clipping to the color value range (0..QuantumRange). See the discussion on
HDRI implementations of ImageMagick on the page High Dynamic-Range Images.
For more about HDRI go the ImageMagick Usage pages or this Wikipedia entry.
-crop geometry
Cut out one or more rectangular regions of the image. See Image Geometry for
complete details about the geometry argument.
The width and height of the geometry argument give the size of the image
that remains after cropping, and x and y in the offset (if present) gives
the location of the top left corner of the cropped image with respect to the
original image. To specify the amount to be removed, use -shave instead.
If the x and y offsets are present, a single image is generated, consisting
of the pixels from the cropping region. The offsets specify the location of
the upper left corner of the cropping region measured downward and rightward
with respect to the upper left corner of the image. If the -gravity option
is present with NorthEast, East, or SouthEast gravity, it gives the distance
leftward from the right edge of the image to the right edge of the cropping
region. Similarly, if the -gravity option is present with SouthWest, South,
or SouthEast gravity, the distance is measured upward between the bottom
edges.
If the x and y offsets are omitted, a set of tiles of the specified
geometry, covering the entire input image, is generated. The rightmost tiles
and the bottom tiles are smaller if the specified geometry extends beyond
the dimensions of the input image.
By adding a exclamation character flag to the geometry argument, the cropped
images virtual canvas page size and offset is set as if the geometry
argument was a viewport or window. This means the canvas page size is set to
exactly the same size you specified, the image offset set relative top left
corner of the region cropped.
If the cropped image 'missed' the actual image on its virtual canvas, a
special single pixel transparent 'missed' image is returned, and a 'crop
missed' warning given.
It might be necessary to +repage the image prior to cropping the image to
ensure the crop coordinate frame is relocated to the upper-left corner of
the visible image.
-cycle amount
displace image colormap by amount. Amount defines the number of positions
each colormap entry is shifted.
-debug events
enable debug printout. The events parameter specifies which events are to be
logged. It can be either None, All, Trace, or a comma-separated list
consisting of one or more of the following domains: Annotate, Blob, Cache,
Coder, Configure, Deprecate, Exception, Locale, Render, Resource, Security,
TemporaryFile, Transform, X11, or User.
For example, to log cache and blob events, use.
$magick> convert -debug "Cache,Blob" rose: rose.png
The User domain is normally empty, but developers can log user events in
their private copy of ImageMagick.
To print the complete list of debug methods, use -list debug.
Use the -log option to specify the format for debugging output.
Use +debug to turn off all logging.
Debugging may also be set using the MAGICK_DEBUG environment variable. The
allowed values for the MAGICK_DEBUG environment variable are the same as for
the -debug option.
-decipher filename
Decipher and restore pixels that were previously transformed by -encipher.
Get the passphrase from the file specified by filename.
For more information, see the webpage, ImageMagick: Encipher or Decipher an
Image.
-deconstruct
find areas that has changed between images Given a sequence of images all
the same size, such as produced by -coalesce, replace the second and later
images, with a smaller image of just the area that changed relative to the
previous image.
The resulting sequence of images can be used to optimize an animation
sequence, though will not work correctly for GIF animations when parts of
the animation can go from opaque to transparent.
This option is actually equivalent to the -layers method 'compare-any'.
-define key{=value}...
add coder/decoder specific options. This option creates one or more
definitions for coders and decoders to use while reading and writing image
data. Definitions may be passed to coders and decoders to control options
that are specific to certain image formats. If value is missing for a
definition, an empty-valued definition of a flag is created with that name.
This used to control on/off options. Use +define key to remove definitions
previously created. Use +define "*" to remove all existing definitions.
The following definitions may be created:
dcm:display-range=reset Set the display range to the minimum and maximum
pixel values for the DCM image format.
dot:layout-engine=value Set the specify the layout engine for the DOT image
format (e.g. neato).
jpeg:extent=value Restrict the maximum JPEG file size, for example -define
jpeg:extent=400kb.
jpeg:size=geometry Set the size hint of a JPEG image, for example, -define
jpeg:size=128x128. It is most useful for increasing performance and reducing
the memory requirements when reducing the size of a large JPEG image.
jp2:rate=value Specify the compression factor to use while writing JPEG-2000
files. The compression factor is the reciprocal of the compression ratio.
The valid range is 0.0 to 1.0, with 1.0 indicating lossless compression. If
defined, this value overrides the -quality setting. A quality setting of 75
results in a rate value of 0.06641.
mng:need-cacheoff turn playback caching off for streaming MNG.
png:bit-depth=value png:color-type=value desired bit-depth and color-type
for PNG output. You can force the PNG encoder to use a different bit-depth
and color-type than it would have normally selected, but only if this does
not cause any loss of image quality. Any attempt to reduce image quality is
treated as an error and no PNG file is written. E.g., if you have a 1-bit
black-and-white image, you can use these "defines" to cause it to be written
as an 8-bit grayscale, indexed, or even a 64-bit RGBA. But if you have a
16-million color image, you cannot force it to be written as a grayscale or
indexed PNG. If you wish to do this, you must use the appropriate -depth,
-colors, or -type directives to reduce the image quality prior to using the
PNG encoder. Note that in indexed PNG files, "bit-depth" refers to the
number of bits per index, which can range from 1 to 8. In such files, the
color samples always have 8-bit depth.
ps:imagemask If the ps:imagemask flag is defined, the PS3 and EPS3 coders
will create Postscript files that render bilevel images with the Postscript
imagemask operator instead of the image operator.
quantum:format=type Set the type to floating-point to specify a single
precision floating-point format for raw files (e.g. GRAY:). For example, to
create a postscript file that will render only the black pixels of a bilevel
image, use:
$magick> convert bilevel.tif -define ps:imagemask eps3:stencil.ps
Set attributes of the image registry by prefixing the value with registry:.
For example, to set a temporary path to put work files, use:
-define registry:temporary-path=/data/tmp
-delay ticks -delay ticksxticks-per-second {<} {>}
display the next image after pausing. This option is useful for regulating
the animation of image sequences ticks/ticks-per-second seconds must expire
before the display of the next image. The default is no delay between each
showing of the image sequence. The default ticks-per-second is 100.
Use > to change the image delay only if its current value exceeds the given
delay. < changes the image delay only if current value is less than the
given delay. For example, if you specify 30> and the image delay is 20, the
image delay does not change. However, if the image delay is 40 or 50, the
delay it is changed to 30. Enclose the given delay in quotation marks to
prevent the < or > from being interpreted by your shell as a file
redirection.
-delete index
delete the image, specified by its index, from the image sequence. Specify
the image by its index in the sequence. The first image is index 0. Negative
indexes are relative to the end of the sequence, for example, -1 represents
the last image of the sequence. Specify a range of images with a dash (e.g.
0-4). Separate indexes with a comma (e.g. 0,2). Use +delete to delete the
last image in the current image sequence.
-density width -density widthxheight
Set the horizontal and vertical resolution of an image for rendering to
devices. This option specifies the image resolution to store while encoding
a raster image or the canvas resolution while rendering (reading) vector
formats such as Postscript, PDF, WMF, and SVG into a raster image. Image
resolution provides the unit of measure to apply when rendering to an output
device or raster image. The default unit of measure is in dots per inch
(DPI). The -units option may be used to select dots per centimeter instead.
The default resolution is 72 dots per inch, which is equivalent to one point
per pixel (Macintosh and Postscript standard). Computer screens are normally
72 or 96 dots per inch, while printers typically support 150, 300, 600, or
1200 dots per inch. To determine the resolution of your display, use a ruler
to measure the width of your screen in inches, and divide by the number of
horizontal pixels (1024 on a 1024x768 display).
If the file format supports it, this option may be used to update the stored
image resolution. Note that Photoshop stores and obtains image resolution
from a proprietary embedded profile. If this profile is not stripped from
the image, then Photoshop will continue to treat the image using its former
resolution, ignoring the image resolution specified in the standard file
header.
The -density option sets an attribute and does not alter the underlying
raster image. It may be used to adjust the rendered size for desktop
publishing purposes by adjusting the scale applied to the pixels. To resize
the image so that it is the same size at a different resolution, use the
-resample option.
-depth value
depth of the image. This the number of bits in a color sample within a
pixel. Use this option to specify the depth of raw images whose depth is
unknown such as GRAY, RGB, or CMYK, or to change the depth of any image
after it has been read.
-descend
obtain image by descending window hierarchy. -deskew threshold
straighten an image. A threshold of 40% works for most images. Use -set
option:deskew:auto-crop width to auto crop the image. The set argument is
the pixel width of the image background (e.g 40).
-despeckle
reduce the speckles within an image. -displace horizontal-scale -displace
horizontal-scalexvertical-scale
shift image pixels as defined by a displacement map. [composite] With
this option, the 'overlay' image, and optionally the 'mask' image, will be
used as a displacement map, which is used to displace the lookup of what
part of the 'background' image is seen at each point of the overlaid area.
Much like the displacement map is a 'lens' that redirects light shining
through it so as to present a distorted view the original 'background' image
behind it.
Any perfect grey areas of the displacement map produce a zero displacement
of the image. Black areas produce the given maximum negative displacement of
the lookup point, while white produce a maximum positive displacement of the
lookup.
Note that it is the lookup of the 'background' that is displaced, not a
displacement of the image itself. As such an area of the displacement map
containing 'white' will have the lookup point 'shifted' by a positive
amount, and thus generating a copy of the destination image to the
right/downward from the correct position. That is the image will look like
it may have been 'shifted' in a negative left/upward direction.
Understanding this is a very important in understanding how displacement
maps work.
The given arguments define the maximum amount of displacement in pixels that
a particular map can produce. If the displacement scale is large enough it
is also posible to lookup parts of the 'background' image that lie well
outside the bounds of the displacement map itself. That is you could very
easilly copy a section of the original image from outside the overlay area
into the overlay area.
The '%' flag makes the displacement scale relative to the size of the
overlay image (100% = half width/height of image). Using '!' switches
percentage arguments to refer to the destination image size instead. these
flags were added as of IM v6.5.3-5.
Normally a single grayscale displacement map is provided, which with the
given scaling values will determine a single direction (vector) in which
displacements can occur (positivally or negativally). However, if you also
specify a third image which is normally used as a mask, then the composite
image will be used for horizontal X displacement, while the mask image is
used for vertical Y displacement. This allows you to define completely
different displacement values for the X and Y directions, and allowing you
to lookup any point within the scale bounds. In other words each pixel can
lookup any other nearby pixel, producing complex 2 dimentional
displacements, rather than a simple 1 dimentional vector displacements.
Alternativally rather than suppling two separate images, as of IM v6.4.4-0,
you can use the 'red' channel of the overlay image to specify the horizontal
or X displacement, and the 'green' channel for the vertical or Y
displacement.
As of IM v6.5.3-5 any alpha channel in the overlay image will be used as a
mask the transparency of the destination image. However areas outside the
overlaid areas will not be effected.
-display host:display[.screen]
Specifies the X server to contact. [animate, display] This option is used
with convert for obtaining image or font from this X server. See X(1).
-dispose method
define the GIF disposal image setting for images that are being created or
read in. The layer disposal method defines the way each the displayed image
is to be modified after the current 'frame' of an animation has finished
being displayed (after its 'delay' period), but before the next frame on an
animation is to be overlaid onto the display.
Here are the valid methods:
Undefined 0 No disposal specified (equivalent to 'none'). None 1
Do not dispose, just overlay next frame image. Background 2 Clear the
frame area with the background color. Previous 3 Clear to the image
prior to this frames overlay. You can also use the numbers given above,
which is what the GIF format uses internally to represent the above
settings.
To print a complete list of dispose methods, use -list dipose.
Use +dispose, turn off the setting and prevent resetting the layer disposal
methods of images being read in.
Use -set 'dispose' method to set the image disposal method for images
already in memory.
-dissimilarity-threshold value
maximum RMSE for subimage match (default 0.2). [compare] -dissolve
src_percent[xdst_percent]
dissolve an image into another by the given percent. [composite] The
opacity of the composite image is multiplied by the given percent, then it
is composited 'over' the main image. If src_percent is greater than 100,
start dissolving the main image so it will become transparent at a value of
'200'. If both percentages are given, each image are dissolved to the
percentages given.
Note that dissolve percentages do not add, two opaque images dissolved
'50,50', produce a 75% transparency. For a 50% + 50% blending of the two
images, you would need to use dissolve values of '50,100'.
-distort method arguments
distort an image, using the given method and its required arguments. The
arguments is a single string containing a list of floating point numbers
separated by commas or spaces. The number of and meaning of the floating
point values depends on the distortion method being used.
Choose from these distortion types:
Method Description ScaleRotateTranslate or SRT Distort image by
first scaling and rotating about a given 'center', before translating that
'center' to the new location, in that order. It is an alternative method of
specifying a 'Affine' type of distortion, but without shearing effects. It
also provides a good way of rotating and displacing a smaller image for
tiling onto a larger background (IE 2-dimensional animations). The number of
arguments determine the specific meaning of each argument for the scales,
rotation, and translation operations. # arguments meaning
1: Angle_of_Rotation 2: Scale Angle 3: ScaleX,ScaleY Angle
4: X,Y Scale Angle 5: X,Y ScaleX,ScaleY Angle 6: X,Y
Scale Angle NewX,NewY 7: X,Y ScaleX,ScaleY Angle NewX,NewY This
is actually an alternative way of specifing a 2 dimensional linear 'Affine'
or 'AffineProjection' distortion. Affine Distort the image linearly by
moving a list of at least 3 or more sets of control points (as defined
below). Idealy 3 sets or 12 floating point values are given allowing the
image to be linearly scaled, rotated, sheared, and translated, according to
those three points. See also the related 'AffineProjection' and 'SRT'
distortions. More than 3 sets given control point pairs (12 numbers) is
least squares fitted to best match a lineary affine distortion. If only 2
control point pairs (8 numbers) are given a two point image translation
rotation and scaling is performed, without any posible shearing, flipping or
changes in aspect ratio to the resulting image. If only one control point
pair is provides the image is only translated, (which may be a floating
point non-integer translation). This distortion does not include any form of
perspective distortion. AffineProjection Linearly distort an image using
the given Affine Matrix of 6 pre-calculated coefficients forming a set of
Affine Equations to map the source image to the destination image. sx, rx,
ry, sy, tx, ty See -affine setting for more detail, and meanings of these
coefficients. The distortions 'Affine' and 'SRT' provide alternative methods
of defining this distortion, with ImageMagick doing the calculations needed
to generate the required coefficients. You can see the internally generated
coefficients, by using a -verbose setting. Perspective Perspective
distort the images, using a list of 4 or more sets of control points (as
defined below). More that 4 sets (16 numbers) of control points provide
least squares fitting for more accurate distortions (for the purposes of
image registration and panarama effects). Less than 4 sets will fall back to
a 'Affine' linear distortion. Perspective Distorted images ensures that
straight lines remain straight, but the scale of the distorted image will
vary. The horizon is anti-aliased, and the 'sky' color may be set using the
-mattecolor setting. PerspectiveProjection Do a 'Perspective'
distortion basied on a set of 8 pre-calculated coefficients. You can get
these coefficients by looking at the -verbose output of a 'Prespective'
distortion, or by calculating them yourself. If the last two perspective
scaling coefficients are zero, the remaining 6 represents a transposed
'Affine Matrix'. Arc Arc the image (variation of polar mapping) over the
angle given around a circle. Argument Meaning arc_angle The angle over
which to arc the image side-to-side rotate_angle Angle to rotate
resulting image from vertical center top_radius Set top edge of source
image at this radius bottom_radius Set bottom edge to this radius
(radial scaling) The resulting image is always resized to best fit the
resulting image, (as if using +distort) while attempting to preserve scale
and aspect ratio of the original image as much as possible with the
arguments given by the user. All four arguments will be needed to change the
overall aspect ratio of an 'Arc'ed image. This a variation of a polar
distortion designed to try to preserve the aspect ratio of the image rather
than direct Cartesian to Polar conversion. Polar Like 'Arc' but do a
complete Cartesian to Polar mapping of the image. that is the height of the
input image is mapped to the radius limits, while the width is wrapped
around between the angle limits. Arguments: Rmax,Rmin CenterX,CenterY,
start,end_angle All arguments are optional. With Rmin defaulting to zero,
the center to the center of the image, and the angles going from -180 (top)
to +180 (top). If Rmax is given the special value of '0', the the distance
from the center to the nearest edge is used for the radius of the output
image, which will ensure the whole image is visible (though scaled smaller).
However a special value of '-1' will use the distance from the center to the
furthest corner, This may 'clip' the corners from the input rectangular
image, but will generate the exact reverse of a 'DePolar' with the same
arguments. If the plus form of distort (+distort) is used output image
center will default to 0,0 of the virtual canvas, and the image size
adjusted to ensure the whole input image is made visible in the output image
on the virtual canvas. DePolar Uses the same arguments and meanings as a
'Polar' distortion but generates the reverse Polar to Cartesian distortion.
The special Rmax setting of '0' may however clip the corners of the input
image. However using the special Rmax setting of '-1' (maximum center to
corner distance) will ensure the whole distorted image is preserved in the
generated result, so that the same argument to 'Polar' will reverse the
distortion re-producing the original. Note that as this distortion requires
the area resampling of a circular arc, which can not be handled by the
builtin EWA resampling function. As such the normal EWA filters are turned
off. It is recomended some form of 'super-sampling' image processing
technique be used to produce a high quality result. Barrel Given the
four coefficients (A,B,C,D) as defined by Helmut Dersch, perform a barrell
or pincussion distortion appropriate to correct radial lens distortions.
That is in photographs, make straight lines straight again. Arguments: A B
C [ D [ X , Y ] ] or Ax Bx Cx Dx Ay By Cy Dy [ X , Y ] So that it
forms the function Rsrc = r * ( A*r3 + B*r2 + C*r + D ) Where X,Y is the
optional center of the distortion (defaulting to the center of the image).
The second form is typically used to distort images, rather than correct
lens distortions. BarrelInverse This is very simular to 'Barrel' with
the same set of arguments, and argument handling. However it uses the
inverse of the radial polynomial, so that it forms the function Rsrc = r / (
A*r3 + B*r2 + C*r + D ) Shepards Distort the given list control points
(any number) using an Inverse Squared Distance Interpolation Method
(Shepards Method). The control points in effect do 'localized' distortions
of the image around the given control point. For best results extra control
points should be added to 'lock' the positions of the corners and other
unchanging parts of the image. The distortion has been likened to 'taffy
pulling' using nails, pins or sticks. It basically uses the -sparse-color
method of the same name to generate separate X and Y displacement maps (see
-displace) for source image color look-up. To print a complete list of
distortion methods, use -list distort.
Many of the above distortion methods such as 'Affine', 'Perspective', and
'Shepards' use a list control points defining how these points in the given
image should be distorted in the destination image. Each set of four
floating point values represent a source image coordinate, followed
immediately by the destination image coordinate. This produces a list of
values such as...
U1,V1 X1,Y1 U2,V2 X2,Y2 U3,V3 X3,Y3 ... Un,Vn Xn,Yn where U,V on the
source image is mapped to X,Y on the destination image.
For example, to warp an image using 'perspective' distortion, needs a list
of at least 4 sets of coordinates, or 16 numbers. Here is the perspective
distortion of the built-in "rose:" image. Note how spaces were used to group
the 4 sets of coordinate pairs, to make it easier to read and understand.
$magick> convert rose: -virtual-pixel black \ -distort Perspective '0,0,0,0
0,45,0,45 69,0,60,10 69,45,60,35' \ rose_3d_rotated.gif
If more that the required number of coordinate pairs are given for a
distortion, the distortion method is 'least squares' fitted to produce the
best result for all the coordinate pairs given. If less than the ideal
number of points are given, the distort will generally fall back to a
simpler form of distortion that can handles the smaller number of
coordinates (usally a linear 'Affine' distortion).
By using more coodinates you can make use of image registration tool to find
matching coordinate pairs in overlaping images, so as to improve the 'fit'
of the distortion. Of course a bad coordinate pair can also make the 'fit'
worse. Caution is always advised.
Colors are acquired from the source image according to the -interpolate
color lookup setting, when the image is magnified. However if the viewed
image is minified (image becomes smaller), a special area resampling
function (added ImageMagick v6.3.5-9), is used to produce a higher quality
image. For example you can use a 'perspective' distortion to view a
infinitely tiled 'plane' all the way to the horizon.
$magick> convert -size 90x90 pattern:checkerboard -normalize -virtual-pixel
tile \ -distort perspective '0,0,5,45 89,0,45,46 0,89,0,89 89,89,89,89' \
checks_tiled.jpg
Note that a infinitely tiled perspective images involving the horizon can be
very slow to generate due to the use of the high quality 'area resampling'
function (added ImageMagick v6.3.5-9). You can turn off 'area resampling'
using a -filter setting of 'point' (recommended if you plan to use
super-sampling instead).
If an image generates invalid pixels, such as the 'sky' in the last
'perspective' distortion example, -distort will use the current -mattecolor
setting for these pixels. If you do not what these pixels to be visible, set
the color to match the rest of the ground.
The output image size will by default be the same as the input image. This
means that if the part of the distorted image falls outside the viewed area
of the 'distorted space', those parts is clipped and lost. However if you
use the plus form of the operator (+distort) the operator will attempt (if
posible) to show the whole of the distorted image, while retaining a correct
'virtual canvas' offset, for image layering. This offset may need to be
removed using +repage, to remove if it is unwanted.
You can alternatively specify a special "-set option:distort:viewport
{geometry_string}" setting which will specify the size and the offset of the
generated 'viewport' image of the distorted image space.
Adding a "-set option:distort:scale {scale_factor}" will scale the output
image (viewport or otherwise) by that factor without changing the viewed
contents of the distorted image. This can be used either for
'super-sampling' the image for a higher quality result, or for panning and
zooming around the image (with appropriate viewport changes, or post-distort
cropping and resizing).
Setting -verbose setting, will cause -distort to attempt to output the
internal coefficients, and the -fx equivalent to the distortion, for expert
study, and debugging purposes. This many not be available for all distorts.
Affine rotations and shears (such as 'SRT' distortion), tend to produce a
cleaner result that the equivalent -rotate and/or -shear operation, with
more control of due to the above settings. It is algorithmically slower,
though in ImageMagick it may be faster.
-dither method
Apply a Riemersma or Floyd-Steinberg error diffusion dither to images when
general color reduction is applied via an option, or automagically when
saving to specific formats. This enabled by default. Dithering places two or
more colors in neighbouring pixels so that to the eye a closer approximation
of the images original color is reproduced. This reduces the number of
colors needed to reproduce the image but at the cost of a lower level
pattern of colors. Error diffusion dithers can use any set of colors
(generated or user defined) to an image.
Dithering is turned on by default, to turn it off use the plus form of the
setting, +dither. This will also also render PostScript without text or
graphic aliasing. Disabling dithering often (but not always) leads to faster
process, a smaller number of colors, but more cartoon like image coloring.
Generally resulting in 'color banding' effects in areas with color
gradients.
The color reduction operators -colors, -monochrome, -remap, and -posterize,
apply dithering to images using the reduced color set they created. These
operators are also used as part of automatic color reduction when saving
images to formats with limited color support, such as GIF:, XBM:, and
others, so dithering may also be used in these cases.
Alternatively you can use -random-threshold to generate purely random
dither. Or use -ordered-dither to apply threshold mapped dither patterns,
using uniform color maps, rather than specific color maps.
-draw string
Annotate an image with one or more graphic primitives. Use this option to
annotate or decorate an image with one or more graphic primitives. The
primitives include shapes, text, transformations, and pixel operations.
The shape primitives:
point x,y line x0,y0 x1,y1 rectangle x0,y0 x1,y1
roundRectangle x0,y0 x1,y1 wc,hc arc x0,y0 x1,y1 a0,a1 ellipse
x0,y0 rx,ry a0,a1 circle x0,y0 x1,y1 polyline x0,y0
... xn,yn polygon x0,y0 ... xn,yn bezier x0,y0 ...
xn,yn path path specification image operator x0,y0 w,h
filename The text primitive:
text x0,y0 string The text gravity primitive:
gravity NorthWest, North, NorthEast, West, Center, East, SouthWest,
South, or SouthEast The text gravity primitive only affects the placement of
text and does not interact with the other primitives. It is equivalent to
using the -gravity command-line option, except that it is limited in scope
to the -draw option in which it appears.
The transformation primitives:
rotate degrees translate dx,dy scale sx,sy skewX
degrees skewY degrees The pixel operation primitives:
color x0,y0 method matte x0,y0 method The shape
primitives are drawn in the color specified by the preceding -fill setting.
For unfilled shapes, use -fill none. You can optionally control the stroke
(the "outline" of a shape) with the -stroke and -strokewidth settings.
A point primitive is specified by a single point in the pixel plane, that
is, by an ordered pair of integer coordinates, x,y. (As it involves only a
single pixel, a point primitive is not affected by -stroke or -strokewidth.)
A line primitive requires a start point and end point.
A rectangle primitive is specified by the pair of points at the upper left
and lower right corners.
A roundRectangle primitive takes the same corner points as a rectangle
followed by the width and height of the rounded corners to be removed.
The circle primitive makes a disk (filled) or circle (unfilled). Give the
center and any point on the perimeter (boundary).
The arc primitive is used to inscribe an elliptical segment in to a given
rectangle. An arc requires the two corners used for rectangle (see above)
followed by the start and end angles of the arc of the segment segment (e.g.
130,30 200,100 45,90). The start and end points produced are then joined
with a line segment and the resulting segment of an ellipse is filled.
Use ellipse to draw a partial (or whole) ellipse. Give the center point, the
horizontal and vertical "radii" (the semi-axes of the ellipse) and start and
end angles in degrees (e.g. 100,100 100,150 0,360).
The polyline and polygon primitives require three or more points to define
their perimeters. A polyline is simply a polygon in which the final point is
not stroked to the start point. When unfilled, this is a polygonal line. If
the -stroke setting is none (the default), then a polyline is identical to a
polygon.
A coordinate is a pair of integers separated by a space or optional comma.
As an example, to define a circle centered at 100,100 that extends to
150,150 use:
-draw 'circle 100,100 150,150'
The Bezier primitive creates a spline curve and requires three or points to
define its shape. The first and last points are the knots and these points
are attained by the curve, while any intermediate coordinates are control
points. If two control points are specified, the line between each end knot
and its sequentially respective control point determines the tangent
direction of the curve at that end. If one control point is specified, the
lines from the end knots to the one control point determines the tangent
directions of the curve at each end. If more than two control points are
specified, then the additional control points act in combination to
determine the intermediate shape of the curve. In order to draw complex
curves, it is highly recommended either to use the path primitive or to draw
multiple four-point bezier segments with the start and end knots of each
successive segment repeated. For example:
-draw 'bezier 20,50 45,100 45,0 70,50'
-draw 'bezier 70,50 95,100 95,0 120,50'
A path represents an outline of an object, defined in terms of moveto (set a
new current point), lineto (draw a straight line), curveto (draw a Bezier
curve), arc (elliptical or circular arc) and closepath (close the current
shape by drawing a line to the last moveto) elements. Compound paths (i.e.,
a path with subpaths, each consisting of a single moveto followed by one or
more line or curve operations) are possible to allow effects such as donut
holes in objects. (See Paths.)
Use image to composite an image with another image. Follow the image keyword
with the composite operator, image location, image size, and filename:
-draw 'image SrcOver 100,100 225,225 image.jpg'
You can use 0,0 for the image size, which means to use the actual dimensions
found in the image header. Otherwise, it is scaled to the given dimensions.
See -compose for a description of the composite operators.
Use text to annotate an image with text. Follow the text coordinates with a
string. If the string has embedded spaces, enclose it in single or double
quotes.
For example, the following annotates the image with Works like magick! for
an image titled bird.miff.
-draw 'text 100,100 "Works like magick!"'
See the -annotate option for another convenient way to annotate an image
with text.
The rotate primitive rotates subsequent shape primitives and text primitives
about the origin of the main image. If the -region option precedes the -draw
option, the origin for transformations is the upper left corner of the
region.
The translate primitive translates subsequent shape and text primitives.
The scale primitive scales them.
The skewX and skewY primitives skew them with respect to the origin of the
main image or the region.
The transformations modify the current affine matrix, which is initialized
from the initial affine matrix defined by the -affine option.
Transformations are cumulative within the -draw option. The initial affine
matrix is not affected; that matrix is only changed by the appearance of
another -affine option. If another -draw option appears, the current affine
matrix is reinitialized from the initial affine matrix.
Use the color primitive to change the color of a pixel to the fill color
(see -fill). Follow the pixel coordinate with a method:
point replace floodfill filltoborder reset Consider the target pixel as that
specified by your coordinate. The point method recolors the target pixel.
The replace method recolors any pixel that matches the color of the target
pixel. Floodfill recolors any pixel that matches the color of the target
pixel and is a neighbor, whereas filltoborder recolors any neighbor pixel
that is not the border color. Finally, reset recolors all pixels.
Use matte to the change the pixel matte value to transparent. Follow the
pixel coordinate with a method (see the color primitive for a description of
methods). The point method changes the matte value of the target pixel. The
replace method changes the matte value of any pixel that matches the color
of the target pixel. Floodfill changes the matte value of any pixel that
matches the color of the target pixel and is a neighbor, whereas
filltoborder changes the matte value of any neighbor pixel that is not the
border color (-bordercolor). Finally reset changes the matte value of all
pixels.
You can set the primitive color, font, and font bounding box color with
-fill, -font, and -box respectively. Options are processed in command line
order so be sure to use these options before the -draw option.
Strings that begin with a number must be quoted (e.g. use '1.png' rather
than 1.png).
Drawing primitives conform to the Magick Vector Graphics format.
-edge radius
detect edges within an image. -emboss radius
emboss an image. -encipher filename
Encipher pixels for later deciphering by -decipher. Get the passphrase from
the file specified by filename.
For more information, see the webpage, ImageMagick: Encipher or Decipher an
Image.
-encoding type
specify the text encoding. Choose from AdobeCustom, AdobeExpert,
AdobeStandard, AppleRoman, BIG5, GB2312, Latin 2, None, SJIScode, Symbol,
Unicode, Wansung.
-endian type
Specify endianness (MSB or LSB) of the image. To print a complete list of
endian types, use the -list endian option.
Use +endian to revert to unspecified endianness.
-enhance
Apply a digital filter to enhance a noisy image. -equalize
perform histogram equalization on the image channel-by-channel. To perform
histogram equalization on all channels in concert, transform the image into
some other color space, such as HSL, OHTA, YIQ or YUV, then equalize the
appropriate intensity-like channel, then convert back to RGB.
For example using HSL, we have: ... -colorspace HSL -channel lightness
-equalize -colorspace RGB ...
For YIQ, YUV and OHTA use the red channel. For example, OHTA is a principal
components transformation that puts most of the information in the first
channel. Here we have ... -colorspace OHTA -channel red -equalize
-colorspace RGB ...
-evaluate operator value
Alter channel pixels by evaluating an arithmetic, relational, or logical
expression. (See the -function operator for some multi-parameter functions.
See the -fx operator if more elaborate calculations are needed.)
The behaviors of each operator are summarized in the following list. For
brevity, the numerical value of a "pixel" referred to below is the value of
the corresponding channel of that pixel, while a "normalized pixel" is that
number divided by the maximum (installation-dependent) value QuantumRange.
(If normalized pixels are used, they are restored, following the other
calculations, to the full range by multiplying by QuantumRange.)
operator Summary (see further below for details) Add Add value to
pixels. AddModulus Add value to pixels modulo QuantumRange. And Binary
AND of pixels with value. Cos, Cosine Apply cosine to pixels with
frequency value with 50% bias added. Divide Divide pixels by value.
LeftShift Shift the pixel values left by value bits (i.e., multiply
pixels by 2value). Log Apply scaled logarithm to normalized pixels.
Max Clip pixels at lower bound value. Min Clip pixels at upper bound
value. Multiply Multiply pixels by value. Or Binary OR of pixels with
value. Pow Raise normalized pixels to the power value.
RightShift Shift the pixel values right by value bits (i.e., divide
pixels by 2value). Set Set pixel equal to value. Sin, Sine Apply sine
to pixels with frequency value with 50% bias added. Subtract Subtract
value from pixels. Xor Binary XOR of pixels with value.
Gaussian-noise Impulse-noise Laplacian-noise Multiplicative-noise (These
are equivalent to the corresponding -noise operators.) PoissonNoise
Uniform-noise
Threshold Threshold pixels larger than value. ThresholdBlack Threshold
pixels to zero values equal to or below value. ThresholdWhite Threshold
pixels to maximum values above value. The specified functions are applied
only to each previously set -channel in the image. If necessary, the results
of the calculations are truncated (clipped) to fit in the interval [0,
QuantumRange]. The transparency channel of the image is represented as a
'alpha' values (0 = fully transparent), so, for example, a Divide by 2 of
the alpha channel will make the image semi-transparent. Append the percent
symbol '%' to specify a value as a percentage of the QuantumRange.
To print a complete list of -evaluate operators, use -list evaluate.
The results of the Add, Subtract and Multiply methods can also be achieved
using either the -level or the +level operator, with appropriate argument,
to linearly modify the overall range of color values. Please note, however,
that -level treats transparency as 'matte' values (0 = opaque), while
-evaluate works with 'alpha' values.
AddModulus has been added as of ImageMagick 6.4.8-4 and provides addition
modulo the QuantumRange. It is therefore equivalent to Add unless the
resulting pixel value is outside the interval [0, QuantumRange].
Log has been added as of ImageMagick 6.4.2-1 and works on normalized pixel
values. This a scaled log function. The value used with Log provides a
scaling factor that adjusts the curvature in the graph of the log function.
The formula applied to a normalized value u is below.
log(value × u + 1) / log(value + 1) Pow has been added as of ImageMagick
6.4.1-9, and works on normalized pixel values. Note that Pow is related to
the -gamma operator. For example, -gamma 2 is equivalent to -evaluate pow
0.5, i.e., a 'square root' function. The value used with -gamma is simply
the reciprocal of the value used with Pow.
Cosine and Sine was added as of IM v6.4.8-8 and converts the image values
into a value according to a (co)sine wave function. The synonyms Cos and Sin
may also be used. The output is biased 50% and normalized by 50% so as to
fit in the respective color value range. The value scaling of the period of
the function (its frequency), and thus determines the number of 'waves' that
will be generated over the input color range. For example, if the value is
1, the effective period is simply the QuantumRange; but if the value is 2,
then the effective period is the half the QuantumRange.
0.5 + 0.5 × cos(2 π u × value). See also the -function operator, which is a
multi-value version of evaluate. -extent geometry
Set the image size and offset. If the image is enlarged, unfilled areas are
set to the background color. To position the image, use offsets in the
geometry specification or precede with a -gravity setting. To specify how to
compose the image with the background, use -compose.
See Image Geometry for complete details about the geometry argument.
-extract geometry
Extract the specified area from image. This option is most useful for
extracting a subregion of a very large raw image. Note that these two
commands are equivalent:
$magick> convert -size 16000x16000 -depth 8 -extract 640x480+1280+960
image.rgb image.png $magick> convert -size 16000x16000 -depth 8
'image.rgb[640x480+1280+960]' image.rgb image.png
If you omit the offsets, as in
$magick> convert -size 16000x16000 -depth 8 -extract 640x480 image.rgb
image.png
then the image will be resized to the specified dimensions instead,
equivalent to:
$magick> convert -size 16000x16000 -depth 8 -resize 640x480 image.rgb
image.png
See Image Geometry for complete details about the geometry argument.
-family fontFamily
Set a font family for text. This setting suggests a font family that
ImageMagick should try to use for rendering text. If the family can be found
it is used; if not, a default font (e.g., "Arial") or a family known to be
similar is substituted (e.g., "Courier" might be used if "System" is
requested but not found).
For other settings that affect fonts, see the options -font, -stretch,
-style, and -weight.
-features distance
display features for each channel in the image in each of four directions
(horizontal, vertical, left and right diagonals) for the specified distance.
-fft
implements the forward discrete Fourier transform (DFT). This option is new
as of ImageMagick 6.5.4-3 and transforms an image from the normal (spatial)
domain to the frequency domain. In the frequency domain, an image is
represented as a superposition of complex sinusoidal waves of varying
amplitudes. The image x and y coordinates are the possible frequencies along
the x and y directions, respectively, and the pixel intensity values are
complex numbers that correspond to the sinusoidal wave amplitudes. See for
example, Fourier Transform, Discrete Fourier Transform and Fast Fourier
Transform.
A single image name is provided as output for this option. However, the
output result will have two components. It will be either a two-frame image
or two separate images, depending upon whether the image format specified
supports multi-frame images. The reason that we get a dual output result is
because the frequency domain represents an image using complex numbers,
which cannot be visualized directly. Therefore, the complex values are
automagically separated into a two-component image representation. The first
component is the magnitude of the complex number and the second is the phase
of the complex number. See for example, Complex Numbers.
The magnitude and phase component images must be specified using image
formats that do not limit the color or compress the image. Thus, MIFF, TIF,
PFM, EXR and PNG are the recommended image formats to use. All of these
formats, except PNG support multi-frame images. So for example,
$magick> convert image.png -fft fft_image.miff
generates a magnitude image as fft_image.miff[0] and a phase image as
fft_image.miff[1]. Similarly,
$magick> convert image.png -fft fft_image.png
generates a magnitude image as fft_image-0.png and a phase image as
fft_image-1.png. If you prefer this representation, then you can force any
of the other formats to produce two output images by including +adjoin
following -fft in the command line.
The input image can be any size, but if not square and even-dimensioned, it
will be padded automagically to the larger of the width or height of the
input image and to an even number of pixels. The padding will occur at the
bottom and/or right sides of the input image. The resulting output magnitude
and phase images will be square at this size. The kind of padding relies on
the -virtual-pixel setting.
Both output components will have dynamic ranges that fit within [0,
QuantumRange], so that HDRI need not be enabled. Phase values nominally
range from 0 to 2*π, but for non-HDRI compilations of ImageMagick, the phase
image is scaled to span the full dynamic range. The magnitude image is not
scaled and thus generally will contain very small values. As such, the image
normally will appear totally black. In order to view any detail, the
magnitude image typically is enhanced with a log function into what is
usually called the spectrum. A log function is used to enhance the darker
values more in comparison to the lighter values. This can be done, for
example, as follows:
$magick> convert fft_image.miff[0] -contrast-stretch 0 \ -evaluate log 1000
fft_image_spectrum.png
where the -contrast-stretch 0 is used to scale the image to full dynamic
range, first. The argument to the -evaluate log typically is specified
between 100 and 10,000, depending upon the amount of detail that one wants
to bring out in the spectrum. Larger values produce more visible detail. Too
much detail, however, may hide the important features.
The FFTW delegate library is required to use -fft.
Use +fft to produce two output images that are the real and imaginary
components of the complex valued Fourier transform.
However, as the real and imaginary components can contain negative values,
this requires that IM be configured with HDRI enabled. In this case, you
must use either MIFF, TIF or PFM formats for the real and imaginary
component results, since they are formats that preserve both negative and
fractional values without clipping them or truncating the fractional part.
The real and imaginary component images resulting from +fft also will be
square, even dimensioned images due to the same padding that was discussed
above for the magnitude and phase component images.
See the discussion on HDRI implementations of ImageMagick on the page High
Dynamic-Range Images. For more about HDRI go the ImageMagick Usage pages or
this Wikipedia entry.
-fill color
color to use when filling a graphic primitive. This option accepts a color
name, a hex color, or a numerical RGB, RGBA, HSL, HSLA, CMYK, or CMYKA
specification. See Color Names for a description of how to properly specify
the color argument.
Enclose the color specification in quotation marks to prevent the "#" or the
parentheses from being interpreted by your shell.
For example,
-fill blue
-fill "#ddddff"
-fill "rgb(255,255,255)"
See -draw for further details.
To print a complete list of color names, use the -list color option.
-filter type
Use this type of filter when resizing an image. Use this option to affect
the resizing operation of an image (see -resize). For example you can use a
simple resize filter such as:
Point Hermite Cubic Box Gaussian Catrom Triangle
Quadratic Mitchell The Bessel and Sinc filter is also provided, but are
by default blackman-windowed. However these filters define a windowing
filter for the Sinc or Bessel filter function, as appropriate for the
scaling operator used (usally Sinc for orthogonal -resize). Windowed filters
include:
Lanczos Hamming Parzen Blackman Kaiser Welsh Hanning
Bartlett Bohman Also one special self-windowing filter is also
provided Lagrange, which will automagically re-adjust its function depending
on the current 'support' or 'lobes' expert settings (see below).
If you do not select a filter with this option, the filter defaults to
Mitchell for a colormapped image, a image with a matte channel, or if the
image is enlarged. Otherwise the filter default to Lanczos.
To print a complete list of resize filters, use the -list filter option.
You can modify how the filter behaves as it scales your image through the
use of these expert settings:
-set filter:blur factor Scale the X axis of the filter (and its window). Use
> 1.0 for blurry or < 1.0 for sharp. -set filter:support radius Set the
filter support radius. -set filter:lobes count Set the number of lobes to
use for the Sinc/Bessel filter. This an alternative way of specifying the
'support' range of the filter. -set filter:b b-spline_factor -set filter:c
keys_alpha_factor Redefine the values used for cubic filters such as Cubic,
Catrom, Mitchel, and Hermite, as well as the Parzen Sinc windowing function.
If only one of the values are defined, the other is set so as to generate a
'Keys' type cubic filter. -set filter:filter filter Use this function
directly as the scaling filter. This will allow you to directly use a
'windowing filter' such as blackman, rather than as its normal usage as a
windowing function for 'Sinc' or 'Bessel'. If defined, no windowing function
is used, unless the following expert setting is also defined. -set
filter:window filter The IIR (infinite impulse response) filters bessel and
sinc are windowed (brought down to zero over the defined support range) with
the given filter. This allows you to use a filter that is not normally used
as a windowing function, such as box, (which effectivally turns off the
windowing function). For example, to get a 8 lobe Lanczos-Bessel filter:
$magick> convert image.png -filter bessel \ -set filter:window=bessel -set
filter:lobes=8 \ -resize 150% image.jpg
Or a raw un-windowed Sinc filter with 4 lobes:
$magick> convert image.png -set filter:filter=sinc -set filter:lobes=4 \
-resize 150% image.jpg
Note that the use of expert options (except for 'blur' with simple resize
filters), are provided for image processing experts who have studied and
understood how resize filters work. Without this knowledge, and an
understanding of the defination of the actual filters involved, using expert
settings are more likely to be detremental to your image resizing.
-flatten
This is a simple alias for the -layers method "flatten". -flip
create a mirror image. reflect the scanlines in the vertical direction.
-floodfill {+-}x{+-}y color
floodfill the image with color at the specified offset. Using -fuzz to
floodfill pixels which only change by a small amount. -flop
create a mirror image. reflect the scanlines in the horizontal direction.
-font name
set the font to use when annotating images with text, or creating labels. To
print a complete list of fonts, use the -list font option (for versions
prior to 6.3.6, use 'type' instead of 'font').
In addition to the fonts specified by the above pre-defined list, you can
also specify a font from a specific source. For example Arial.ttf is a
TrueType font file, ps:helvetica is PostScript font, and x:fixed is X11
font.
For other settings that affect fonts, see the options -family, -stretch,
-style, and -weight.
-foreground color
Define the foreground color. The color is specified using the format
described under the -fill option.
The default foreground color is black.
-format type
the image format type. When used with the mogrify utility, this option
converts any image to the image format you specify. For a list of image
format types supported by ImageMagick, use -list format.
By default the file is written to its original name. However, if the
filename extension matches a supported format, the extension is replaced
with the image format type specified with -format. For example, if you
specify tiff as the format type and the input image filename is image.gif,
the output image filename becomes image.tiff.
-format string
output formatted image characteristics. [identify] See Format and Print
Image Properties for an explanation on how to specify the argument to this
option.
-frame geometry
Surround the image with a border or beveled frame. The color of the border
is specified with the -mattecolor command line option.
See Image Geometry for complete details about the geometry argument. The
size portion of the geometry argument indicates the amount of extra width
and height that is added to the dimensions of the image. If no offsets are
given in the geometry argument, then the border added is a solid color.
Offsets x and y, if present, specify that the width and height of the border
is partitioned to form an outer bevel of thickness x pixels and an inner
bevel of thickness y pixels. (Negative offsets make no sense here.) The
-frame option is not affected by the -gravity option.
-frame
include the X window frame in the imported image. [import] -function
function parameters
Apply a function to channel values. This operator performs calculations
based on the given arguments to modify each of the color values for each
previously set -channel in the image. See -evaluate for details concerning
how the results of the calculations are handled.
This is can be considered a multi-argument version of the -evaluate
operator. (Added in ImageMagick 6.4.8−8.)
Here, parameters is a comma-separated list of numerical values. The number
of values varies depending on which function is selected. Choose the
function from:
Polynomial Sinusoid Arcsin Arctan To print a complete list of -function
operators, use -list function. Descriptions follow.
Polynomial The Polynomial function takes an arbitrary number of parameters,
these being the coefficients of a polynomial, in decreasing order of degree.
That is, entering
-function Polynomial an,an-1,...a1,a0 will invoke a polynomial function
given by
an un + an-1 un-1 + ··· a1 u + a0, where u is pixel's original normalized
channel value.
The Polynomial function can be used in place of Set (the constant
polynomial) and Add, Divide, Multiply, and Subtract (some linear
polynomials) of the -evaluate operator. The -level operator also affects
channels linearly. Some correspondences follow.
-evaluate Set value -function Polynomial value (Constant functions;
set value×100% gray when channels are RGB.) -evaluate Add value -function
Polynomial 1,value -evaluate Subtract value -function Polynomial 1,−value
-evaluate Multiply value -function Polynomial value,0 +level black% x
white% -function Polynomial A,B (Reduce contrast. Here,
A=(white-black)/100 and B=black/100.) The Polynomial function gives great
versatility, since polynomials can be used to fit any continuous curve to
any degree of accuracy desired.
Sinusoid The Sinusoid function can be used to vary the channel values
sinusoidally by setting frequency, phase shift, amplitude, and a bias. These
values are given as one to four parameters, as follows,
-function Sinusoid freq,[phase,[amp,[bias]]] where phase is in degrees. (The
domain [0,1] of the function corresponds to 0 through freq×360 degrees.) The
result is that if a pixel's normalized channel value is originally u, its
resulting normalized value is given by
amp * sin(2*π* (freq * u + phase / 360)) + bias For example, the following
generates a curve that starts and ends at 0.9 (when u=0 and 1, resp.),
oscillating three times between .7−.2=.5 and .7+.2=.9.
-function Sinusoid 3,-90,.2,.7
The default values of amp and bias are both .5. The default for phase is 0.
The Sinusoid function generalizes Sin and Cos of the -evaluate operator by
allowing varying amplitude, phase and bias. The correspondence is as
follows.
-evaluate Sin freq -function Sinusoid freq,0 -evaluate Cos
freq -function Sinusoid freq,90 ArcSin The ArcSin function generates the
inverse curve of a Sinusoid, and can be used to generate cylindrical
distortion and displacement maps. The curve can be adjusted relative to both
the input values and output range of values.
-function ArcSin width,[center,[range,[bias]]] with all values given in
terms of noramlize color values (0.0 for black, 1.0 for white). Defaulting
to values covering the full range from 0.0 to 1.0 for bout input (width),
and output (width) values. '1.0,0.5,1.0,0.5'
range/π * asin( 2/width * ( u - center ) ) + bias ArcTan The ArcTan function
generates a curve that smooth crosses from limit values at infinities,
though a center using the given slope value. All these values can be
adjusted via the arguments.
-function ArcTan slope,[center,[range,[bias]]] Defaulting to
'1.0,0.5,1.0,0.5'.
range/π * atan( slope*π * ( u - center ) ) + bias -fuzz distance{%}
Colors within this distance are considered equal. A number of algorithms
search for a target color. By default the color must be exact. Use this
option to match colors that are close to the target color in RGB space. For
example, if you want to automagically trim the edges of an image with -trim
but the image was scanned and the target background color may differ by a
small amount. This option can account for these differences.
The distance can be in absolute intensity units or, by appending % as a
percentage of the maximum possible intensity (255, 65535, or 4294967295).
-fx expression
apply a mathematical expression to an image or image channels. If the first
character of expression is @, the expression is read from a file titled by
the remaining characters in the string.
See FX, The Special Effects Image Operator for a detailed discussion of this
option.
-gamma value
level of gamma correction. The same color image displayed on two different
workstations may look different due to differences in the display monitor.
Use gamma correction to adjust for this color difference. Reasonable values
extend from 0.8 to 2.3. Gamma less than 1.0 darkens the image and gamma
greater than 1.0 lightens it. Large adjustments to image gamma may result in
the loss of some image information if the pixel quantum size is only eight
bits (quantum range 0 to 255).
Gamma adjusts the image's channel values pixel-by-pixel according to a power
law, namely, pow(pixel,1/gamma) or pixel^(1/gamma), where pixel is the
normalized or 0 to 1 color value. For example, using a value of gamma=2 is
the same as taking the square root of the image.
You can apply separate gamma values to the red, green, and blue channels of
the image with a gamma value list delimited with commas (e.g., 1.7,2.3,1.2).
Use +gamma value to set the image gamma level without actually adjusting the
image pixels. This option is useful if the image is of a known gamma but not
set as an image attribute (e.g. PNG images).
Note that gamma adjustments are also available via the -level operator.
-gaussian-blur radius -gaussian-blur radiusxsigma
Blur the image with a Gaussian operator. Convolve the image with a Gaussian
or normal distribution. The formula is:
where r is the blur radius (r2 = u2 + v2), and σ is the standard deviation
of the Gaussian distribution. As a guideline, set r to approximately 3σ.
Specify a radius of 0 and ImageMagick selects a suitable radius for you.
This differs from the faster -blur operator in that a full 2-dimentional
convolution is used to generate the weighted average of the neighbouring
pixels.
The -virtual-pixel setting will determine how pixels which are outside the
image proper are blurred into the final result.
-geometry geometry
Set the preferred size and location of the image. See Image Geometry for
complete details about the geometry argument.
-gravity type
Sets the current gravity suggestion for various other settings and options.
Choices include: NorthWest, North, NorthEast, West, Center, East, SouthWest,
South, SouthEast. Use -list gravity to get a complete list of -gravity
settings available in your ImageMagick installation.
The direction you choose specifies where to position text or subimages. For
example, a gravity of Center forces the text to be centered within the
image. By default, the image gravity is NorthWest. See -draw for more
details about graphic primitives. Only the text primitive of -draw affected
by the -gravity option.
The -gravity option is also used in concert with the -geometry setting and
other settings or options that take geometry as an argument, such as the
-crop option.
If a -gravity setting occurs before another option or setting having a
geometry argument that specifies an offset, the offset is usually applied to
the point within the image suggested by the -gravity argument. Thus, in the
following command, for example, suppose the file image.png has dimensions
200x100. The offset specified by the argument to -region is (−40,+20). The
argument to -gravity is Center, which suggests the midpoint of the image, at
the point (100,50). The offset (−40,20) is applied to that point, giving
(100−40,50+20)=(60,70), so the specified 10x10 region is located at that
point. (In addition, the -gravity affects the region itself, which is
centered at the pixel coordinate (60,70). (See Image Geometry for complete
details about the geometry argument.)
$magick> convert image.png -gravity Center -region 10x10-40+20 -negate
output.png
When used as an option to composite, -gravity gives the direction that the
image gravitates within the composite.
When used as an option to montage, -gravity gives the direction that an
image gravitates within a tile. The default gravity is Center for this
purpose.
-green-primary x,y
green chromaticity primary point. -hald-clut
apply a Hald color lookup table to the image. A Hald color lookup table is a
3-dimensional color cube mapped to 2 dimensions. Create it with the HALD:
prefix (e.g. HALD:8). You can apply any color transformation to the Hald
image and then use this option to apply the transform to the image.
$magick> convert image.png hald.png -hald-clut transform.png
This option provides a convenient method for you to use Gimp or Photoshop to
make color corrections to the Hald CLUT image and subsequently apply them to
multiple images using an ImageMagick script.
Note that the representation is only of the normal RGB color space and that
the whole color value triplet is used for the interpolated lookup of the
represented Hald color cube image. Because of this the operation is not
-channel setting effected, nor can it adjust or modify an images
transparency or alpha/matte channel.
See also -clut which provides color value replacement of the individual
color channels, usally involving a simplier gray-scale image. E.g:
gray-scale to color replacement, or modification by a histogram mapping.
-help
print usage instructions. -highlight-color color
when comparing images, emphasize pixel differences with this color.
-iconGeometry geometry
specify the icon geometry. Offsets, if present in the geometry
specification, are handled in the same manner as the -geometry option, using
X11 style to handle negative offsets.
See Image Geometry for complete details about the geometry argument.
-iconic
iconic animation. -identify
identify the format and characteristics of the image. This information is
printed: image scene number; image name; image size; the image class
(DirectClass or PseudoClass); the total number of unique colors; and the
number of seconds to read and transform the image. Refer to MIFF for a
description of the image class.
If -colors is also specified, the total unique colors in the image and color
reduction error values are printed. Refer to color reduction algorithm for a
description of these values.
If -verbose preceds this option, copious amounts of image properties are
displayed including image statistics, profiles, image histogram, and others.
-ift
implements the inverse discrete Fourier transform (DFT). This option is new
as of ImageMagick 6.5.4-3 and transforms a pair of magnitude and phase
images from the frequency domain to a single image in the normal or spatial
domain. See for example, Fourier Transform, Discrete Fourier Transform and
Fast Fourier Transform.
For example, depending upon the image format used to store the result of the
-fft, one would use either
$magick> convert fft_image.miff -ift fft_image_ift.png
or
$magick> convert fft_image-0.png fft_image-1.png -ift fft_image_ift.png
The resulting image may need to be cropped due to padding introduced when
the original image, prior to the -fft or +fft, was not square or even
dimensioned. Any padding will be at the right and/or bottom sides of the
image.
The FFTW delegate library is required to use -ift.
Use +ift (with HDRI enabled) to transform a pair of real and imaginary
images from the frequency domain to a single image in the normal (spatial)
domain.
-immutable
make image immutable. -implode factor
implode image pixels about the center. -insert index
insert the last image into the image sequence. This option takes last image
in the current image sequence and inserts it at the given index. If a
negative index is used, the insert position is calculated before the last
image is removed from the sequence. As such -insert -1 will result in no
change to the image sequence.
The +insert option is equivalent to -insert -1. In other words, insert the
last image, at the end of the current image sequence. Consequently this has
no effect on the image sequence order.
-intent type
use this type of rendering intent when managing the image color. Use this
option to affect the color management operation of an image (see -profile).
Choose from these intents: Absolute, Perceptual, Relative, Saturation.
The default intent is undefined.
To print a complete list of rendering intents, use -list intent.
-interlace type
the type of interlacing scheme. Choose from:
none line plane partition JPEG GIF PNG This option is used to specify the
type of interlacing scheme for raw image formats such as RGB or YUV.
None means do not interlace (RGBRGBRGBRGBRGBRGB...),
Line uses scanline interlacing (RRR...GGG...BBB...RRR...GGG...BBB...), and.
Plane uses plane interlacing (RRRRRR...GGGGGG...BBBBBB...).
Partition is like plane except the different planes are saved to individual
files (e.g. image.R, image.G, and image.B).
Use Line or Plane to create an interlaced PNG or GIF or progressive JPEG
image.
To print a complete list of interlacing schemes, use -list interlace.
-interpolate type
Set the pixel color interpolation method to use when looking up a color
based on a floating point or real value. When looking up the color of a
pixel using a non-interger floating point value, you typically fall in
between the pixel colors defined by the source image. This setting
determines how the color is determined from the colors of the pixels
surrounding that point. That is how to determine the color of a point that
falls between two, or even four different colored pixels.
integer: The color of the top-left pixel (floor function)
nearest-neighbor: The nearest pixel to the lookup point (rounded function)
average: The average color of the surrounding four pixels bilinear
A double linear interpolation of pixels (the default) mesh
Divide area into two flat triangular interpolations bicubic
Fitted bicubic-spines of surrounding 16 pixels spline Direct
spline curves (colors are blurred) filter Use resize -filter
settings This most important for distortion operators such as -distort,
-implode, -transform and -fx.
To print a complete list of interpolation methods, use -list interpolate.
See also -virtual-pixel, for control of the lookup for positions outside the
boundaries of the image.
-interline-spacing value
the space between two text lines. -interword-spacing value
the space between two words. -kerning value
the space between two letters. -label name
assign a label to an image. Use this option to assign a specific label to
the image, as it is read in or created. You can use the -set operation to
re-assign a the labels of images already read in. Image formats such as
TIFF, PNG, MIFF, supports saving the label information with the image.
When saving an image to a PostScript file, any label assigned to an image is
used as a header string to print above the postscript image.
You can include the image filename, type, width, height, or other image
attribute by embedding special format character. See -format for details of
the percent escape codes.
For example,
-label "%m:%f %wx%h" bird.miff
assigns an image label of MIFF:bird.miff 512x480 to the "bird.miff" image
and whose width is 512 and height is 480, as it is read in. If a +label
option was used instead, any existing label present in the image would be
used. You can remove all labels from an image by assigning the empty string.
A label is not drawn on the image, but is embedded in the image datastream
via Label tag or similar mechanism. If you want the label to be visible on
the image itself, use the -draw option, or during the final processing in
the creation of a image montage.
The label font can be specified with -font, and the other font attribute
settings.
If the first character of string is @, the image label is read from a file
titled by the remaining characters in the string. Labels in a file are
literal, no embedded formatting characters are recognized.
-lat width -lat widthxheight{+-}offset{%}
perform local adaptive threshold. Adaptively threshold each pixel based on
the value of pixels in a surrounding window. If the current pixel is lighter
than this average plus the optional offset, then it is made white, otherwise
it is made black. Small variations in pixel values such as found in scanned
documents can be ignored if offset is positive. A negative offset will make
it more sensitive to those small variations.
This is commonly used to threshold images with an uneven background. It is
based on the assumption that average color of the small window is the the
local background color, from which to separate the forground color.
-layers method
handle multiple images forming a set of image layers or animation frames.
Perform various image operation methods to a ordered sequence of images
which may represent either a set of overlaid 'image layers', a GIF disposal
animation, or a fully-'coalesced' animation sequence.
Method Description compare-any Crop the second and later frames to the
smallest rectangle that contains all the differences between the two images.
No GIF -dispose methods are taken into account. This exactly the same as the
-deconstruct operator, and does not preserve animations normal working,
especially when animation used layer disposal methods such as 'Previous' or
'Background'. compare-clear As 'compare-any' but crop to the bounds of
any opaque pixels which become transparent in the second frame. That is the
smallest image needed to mask or erase pixels for the next frame.
compare-overlay As 'compare-any' but crop to pixels that add extra color
to the next image, as a result of overlaying color pixels. That is the
smallest single overlaid image to add or change colors. This can be used
with the -compose alpha composition method 'change-mask', to reduce the
image to just the pixels that need to be overlaid. coalesce Equivalent to
a call to the -coalesce operator. Apply the layer disposal methods set in
the current image sequence to form a fully defined animation sequence, as it
should be displayed. Effectively converting a GIF animation into a 'film
strip'-like animation. composite Alpha Composition of two image lists,
separated by a "null:" image, with the destination image list first, and the
source images last. An image from each list are composited together until
one list is finished. The separator image and source image lists are
removed. The -geometry offset is adjusted according to -gravity in
accordance of the virtual canvas size of the first image in each list.
Unlike a normal -composite operation, the canvas offset is also added to the
final composite positioning of each image. If one of the image lists only
contains one image, that image is applied to all the images in the other
image list, regardless of which list it is. In this case it is the image
meta-data of the list which preserved. dispose This like 'coalesce' but
shows the look of the animation after the layer disposal method has been
applied, before the next sub-frame image is overlaid. That is the 'dispose'
image that results from the application of the GIF -dispose method. This
allows you to check what is going wrong with a particular animation you may
be developing. flatten Create a canvas the size of the first images
virtual canvas using the current -background color, and -compose each image
in turn onto that canvas. Images falling outside that canvas is clipped.
Final image will have a zero virtual canvas offset. This usally used as one
of the final 'image layering' operations overlaying all the prepared image
layers into a final image. For a single image this method can also be used
to fillout a virtual canvas with real pixels, or to underlay a opaque color
to remove transparency from an image. merge As 'flatten' method but
merging all the given image layers into a new layer image just large enough
to hold all the image without clipping or extra space. The new images
virtual offset will prevere the position of the new layer, even if this
offset is negative. the virtual canvas size of the first image is preserved.
Caution is advised when handling image layers with negative offsets as few
image file formats handle them correctly. mosaic As 'flatten' method but
expanding the initial canvas size of the first image so as to hold all the
image layers. However as a virtual canvas is 'locked' to the origin, by
defination, image layers with a negative offsets will still be clipped by
the top and left edges. This method is commonly used to layout individual
image using various offset but without knowning the final canvas size. The
resulting image will, like 'flatten' not have any virtual offset, so can be
saved to any image file format. optimize Optimize a coalesced animation,
into GIF animation using a number of general techniques. This currently a
short cut to apply both the 'optimize-frame', and 'optimize-transparency'
methods but may be expanded to include other optimization methods as they
are developed. optimize-frame Optimize a coalesced animation, into GIF
animation by reducing the number of pixels per frame as much as possible by
attempting to pick the best layer disposal method to use, while ensuring the
result will continue to animate properly. There is no guarantee that the
best optimization is found. But then no reasonably fast GIF optimization
algorithm can do this. However this does seem to do better than most other
GIF frame optimizers seen. optimize-plus As 'optimize-frame' but attempt
to improve the overall optimization by adding extra frames to the animation,
without changing the final look or timing of the animation. The frames are
added to attempt to separate the clearing of pixels from the overlaying of
new additional pixels from one animation frame to the next. If this does not
improve the optimization (for the next frame only), it will fall back to the
results of the previous normal 'optimize-frame' technique. There is the
possibility that the change in the disposal style will result in a worsening
in the optimization of later frames, though this is unlikely. In other words
there no guarantee that it is better than the normal 'optimize-frame'
technique. For some animations however you can get a vast improvment in the
final animation size. optimize-transparency Given a GIF animation,
replace any pixel in the sub-frame overlay images with transparency, if it
does not change the resulting animation by more than the current -fuzz
factor. This should allow a existing frame optimized GIF animation to
compress into a smaller file size due to larger areas of one (transparent)
color rather than a pattern of multiple colors repeating the current
disposed image of the last frame. remove-dups Remove (and merge time
delays) of duplicate consecutive images, so as to simplify layer overlays of
coalesced animations. Usually this a result of using a constant time delay
across the whole animation, or after a larger animation was split into
smaller sub-animations. The duplicate frames could also have been used as
part of some frame optimization methods. remove-zero Remove any image
with a zero time delay, unless ALL the images have a zero time delay (and is
not a proper timed animation, a warning is then issued). In a GIF animation,
such images are usually frames which provide partial intermediary updates
between the frames that are actually displayed to users. These frames are
usally added for improved frame optimization in GIF animations.
trim-bounds Find the bounds of all the images in the current image
sequence, then adjust the offsets so all images are contained on a minimal
positive canvas. None of the image data is modified, only there virtual
canvas size and offset. The all the image is given the same canvas size, and
and will have a positive offset, but will remain in the same position
relative to each other. As a result of the minimal canvas size at least one
image will touch every edge of that canvas. The image data however may be
transparent. To print a complete list of layer types, use -list layers.
The operators -coalesce, -deconstruct, -flatten, and -mosaic are only
aliases for the above methods. Also see -page, -repage operators, the
-compose setting, and the GIF -dispose and -delay settings.
-level black_point{,white_point}{%}{,gamma}
adjust the level of image channels. Given one, two or three values delimited
with commas: black-point, white-point, gamma (for example: 10,250,1.0 or
2%,98%,0.5). The black and white points range from 0 to QuantumRange, or
from 0 to 100%; if the white point is omitted it is set to (QuantumRange -
black_point), so as to center contrast changes. If a % sign is present
anywhere in the string, both black and white points are percentages of the
full color range. Gamma will do a -gamma adjustment of the values. If it is
omitted, the default of 1.0 (no gamma correction) is assumed.
In normal usage (-level) the image values are stretched so that the given
'black_point' value in the original image is set to zero (or black), while
the given 'white_point' value is set to QuantumRange (or white). This
provides you with direct contrast adjustments to the image. The 'gamma' of
the resulting image will then be adjusted.
From ImageMagick v6.4.1-9 using the plus form of the operator (+level) or
adding the special '!' flag anywhere in the argument list, will cause the
operator to do the reverse of the level adjustment. That is a zero, or
QuantumRange value (black, and white, resp.) in the original image, is
adjusted to the given level values, allowing you to de-contrast, or compress
the channel values within the image. The 'gamma' is adjusted before the
level adjustment to de-contrast the image is made.
Only the channels defined by the current -channel setting are adjusted
(defaults to RGB color channels only), allowing you to limit the effect of
this operator.
Please note that the transparency channel is treated as 'matte' values (0 is
opaque) and not as 'alpha' values (0 is transparent).
-level-colors {black_color}{,}{white_color}
adjust the level of an image using the provided dash seperated colors. This
function is exactly like -level, except that the value value for each color
channel is determined by the 'black_color' and 'white_color' colors given
(as described under the -fill option).
This effectivally means the colors provided to -level-colors is mapped to
become 'black' and 'white' respectivally, with all the other colors linearly
adjusted (or clipped) to match that change. Each channel is adjusted
separatally using the channel values of the colors specified.
On the other hand the plus form of the operator (+level-colors) will map the
image color 'black' and 'white' to the given colors respectivally, resulting
in a gradient (de-contrasting) tint of the image to those colors. This can
also be used to convert a plain gray-scale image into a one using the
gradient of colors specified.
By supplying a single color with a comma separator either before or after
that color, will just replace the respective 'black' or 'white' point
respectivally. But if no comma separator is provided, the given color is
used for both the black and white color points, making the operator either
threshold the images around that color (- form) or set all colors to that
color (+ form).
-limit type value
Set the pixel cache resource limit. Choose from: area, disk, file, map,
memory, threads, or time.
The value for file is in number of files. The other limits are in bytes. By
default the limits are 768 files, 2GB of image area, 1.5GiB memory, 8GiB
memory map, and 18.45EB of disk. These limits are adjusted relative to the
available resources on your computer if this information is available. When
any limit is reached, ImageMagick fails in some fashion but attempts to take
compensating actions, if possible. For example, the following limits memory:
-limit memory 32MiB -limit map 64MiB
Use -list resource to list the current limits. For example, our system shows
these limits:
$magick> identify -list resource
File Area Memory Map Disk Thread
Time
----------------------------------------------------------------------------
-- 768 12.404GB 8.6642GiB 23.104GiB 18.446744EB 8
unlimited Requests for pixel storage to keep intermediate images are
satisfied by one of three resource categories: in-memory pool, memory-mapped
files pool, and disk pool (in that order) depending on the ‑limit settings
and whether the system honors a resource request. If the total size of
allocated pixel storage in the given pool reaches the corresponding limit,
the request is passed to the next pool. Additionally, requests that exceed
the area limit automagically are allocated on disk.
To illustrate how ImageMagick utilizes resource limits, consider a typical
image resource request. First, ImageMagick tries to allocate the pixels in
memory. The request might be denied if the resource request exceeds the
memory limit or if the system does not honor the request. If a memory
request is not honored, the pixels are allocated to disk and the file is
memory-mapped. However, if the allocation request exceeds the map limit, the
resource allocation goes to disk. In all cases, if the resource request
exceeds the area limit, the pixels are automagically cached to disk. If the
disk has a hard limit, the program fails.
In most cases you simply do not need to concern yourself with resource
limits. ImageMagick chooses reasonable defaults and most images do not tax
your computer resources. Where limits do come in handy is when you process
images that are large or on shared systems where ImageMagick can consume all
or most of the available memory. In this case, the ImageMagick workflow
slows other processes or, in extreme cases, brings the system to a halt.
Under these circumstances, setting limits give some assurances that the
ImageMagick workflow will not interfere with other concurrent uses of the
computer. For example, assume you have a web interface that processes images
uploaded from the Internet. To assure ImageMagick does not exceed 10mb of
memory you can simply set the area limit to 10mb:
-limit area 10mb
Now whenever a large image is processed, the pixels are automagically cached
to disk instead of memory. This of course implies that large images
typically process very slowly, simply because pixel processing in memory can
be an order of magnitude faster than on disk. Because your web site users
might inadvertedly upload a huge image to process, you should set a disk
limit as well:
-limit area 10mb -limit disk 500mb
Here ImageMagick stops processing if an image requires more than 500MB of
disk storage.
In addition to command-line resource limit option, resources can be set with
environment variables. Set the environment variables MAGICK_AREA_LIMIT,
MAGICK_DISK_LIMIT, MAGICK_FILE_LIMIT, MAGICK_MEMORY_LIMIT, MAGICK_MAP_LIMIT,
MAGICK_THREAD_LIMIT, MAGICK_TIME_LIMIT for limits of image area, disk space,
open files, heap memory, memory map, number of threads of execution, and
maximum elapsed time in seconds respectively.
Inquisitive users can try adding -debug cache to their commands and then
scouring the generated output for references to the pixel cache, in order to
determine how the pixel cache was allocated and how resources were consumed.
Advanced Unix/Linux users can pipe that output through grep
memory|open|destroy|disk for more readable sifting.
For more about ImageMagick's use of resources, see the section Cache Storage
and Resource Requirements on the Architecture page.
-linear-stretch black-point -linear-stretch black-point{xwhite-point}{%}}
Linear with saturation stretch. This is very similar to -contrast-stretch,
and uses a 'histogram bin' to determine the range of color values that needs
to be stretched. However it then stretchs those colors using the -level
operator.
As such while the initial determination may have 'binning' round off
effects, the image colors are stretched mathematically, rather than using
the histogram bins. This makes the operator more accurate.
note however that a -linear-stretch of '0' does nothing, while a value of
'1' does a near perfect stretch of the color range.
See also -auto-level for a 'perfect' normalization of mathematical images.
This operator is under review for re-development.
-linewidth
the line width for subsequent draw operations. -liquid-rescale geometry
rescale image with seam-carving. See Image Geometry for complete details
about the geometry argument.
-list type
Print a list of supported arguments for various options or settings. Choose
from these list types: coder color configure delegate font format list log
magic module resource threshold The above lists are only some of the many
lists available. These lists vary depending on your version of ImageMagick.
For example use "-list list" to get a complete listing of all the "-list"
arguments available:
$magick> identify -list list
-log string
Specify format for debug log. This option specifies the format for the log
printed when the -debug option is active.
You can display the following components by embedding special format
characters:
%d domain %e event %f function %l line %m module %p process ID
%r real CPU time %t wall clock time %u user CPU time %% percent sign
\n newline \r carriage return For example:
$magick> convert -debug coders -log "%u %m:%l %e" in.gif out.png
The default behavior is to print all of the components.
-loop iterations
add Netscape loop extension to your GIF animation. Set iterations to zero to
repeat the animation an infinite number of times, otherwise the animation
repeats itself up to iterations times.
-lowlight-color color
when comparing images, de-emphasize pixel differences with this color.
-magnify factor
magnify the image. -map type
Display image using this type. [animate, display] Choose from these
Standard Colormap types:
best default gray red green blue The X server must support the Standard
Colormap you choose, otherwise an error occurs. Use list as the type and
display searches the list of colormap types in top-to-bottom order until one
is located. See xstdcmap(1) for one way of creating Standard Colormaps.
-map components
pixel map. [stream] Here are the valid components of a map:
r red pixel component g green pixel component b blue
pixel component a alpha pixel component (0 is transparent) o
opacity pixel component (0 is opaque) i grayscale intensity pixel
component c cyan pixel component m magenta pixel component y
yellow pixel component k black pixel component p pad
component (always 0) You can specify as many of these components as needed
in any order (e.g. bgr). The components can repeat as well (e.g. rgbr).
-mask filename
Composite the image pixels as defined by the mask. Use +mask to remove the
image mask.
-mattecolor color
Specify the color to be used with the -frame option. The color is specified
using the format described under the -fill option.
The default matte color is #BDBDBD, this shade of gray.
-median radius
apply a median filter to the image. -metric type
Output to STDERR a measure of the differences between images according to
the type given metric. Choose from:
AE absolute number of differnet pixels MAE mean absolute error
(normalized), average channel error distance MEPP mean error per pixel
(normalized mean error, normalized peak error) MSE mean error squared,
average of the channel error squared PAE peak absolute (normalize peak
absolute) PSNR peak signal to noise ratio RMSE root mean squared
(normalized root mean squared) The 'AE' or absolute count of pixels that are
different, can be controled using a -fuzz factor to ignore pixels which only
changed by a small amount. The 'PAE' can be used to find the size of the
-fuzz factor needed to make all pixels 'similar'.
The 'MEPP' metric returns three different metrics ('MAE', 'MAE' normalized,
and 'PAE' normalized) from the single comparision run.
To print a complete list of metrics, use the -list metrics option.
-mode value
Mode of operation. [montage] Choose the value from these styles: Frame,
Unframe, or Concatenate
Use the -list option with a 'Mode' argument for a list of -mode arguments
available in your ImageMagick installation.
-modulate brightness[,saturation,hue]
Vary the brightness, saturation, and hue of an image. The arguments are
given as a percentages of variation. A value of 100 means no change, and any
missing values are taken to mean 100.
The brightness is a multiplier of the overall brightness of the image, so 0
means pure black, 50 is half as bright, 200 is twice as bright. To invert
its meaning -negate the image before and after.
The saturation controls the amount of color in an image. For example, 0
produce a grayscale image, while a large value such as 200 produce a very
colorful, 'cartoonish' color.
The hue argument causes a "rotation" of the colors within the image by the
amount specified. For example, 50 results in a counter-clockwise rotation of
90, mapping red shades to purple, and so on. A value of either 0 or 200
results in a complete 180 degree rotation of the image. Using a value of 300
is a 360 degree rotation resulting in no change to the original image.
For example, to increase the color brightness by 20% and decrease the color
saturation by 10% and leave the hue unchanged, use -modulate 120,90.
Use -set attribute of 'option:modulate:colorspace' to specify which
colorspace to modulate. Choose from HSB, HSL (the default), or HWB. For
example,
$magick> convert image.png -set option:modulate:colorspace hsb -modulate
120,90 modulate.png
-monitor
monitor progress. -monochrome
transform the image to black and white. -morph frames
morphs an image sequence. Both the image pixels and size are linearly
interpolated to give the appearance of a meta-morphosis from one image to
the next, over all the images in the current image list. The added images
are the equivalent of a -blend composition. The frames argument determine
how many images to interpolate between each image.
-morphology
-morphology method kernel
apply a morphology method to the image -mosaic
an simple alias for the -layers method "mosaic" -motion-blur radius
-motion-blur radiusxsigma+angle
simulate motion blur. Blur with the given radius, standard deviation
(sigma), and angle. The angle given is the angle toward which the image is
blurred. That is the direction people would consider the object is coming
from.
Note that the blur is not uniform distribution, giving the motion a definate
sense of direction of movement.
The -virtual-pixel setting will determine how pixels which are outside the
image proper are blurred into the final result.
-name
name an image. -negate
replace each pixel with its complementary color. The red, green, and blue
intensities of an image are negated. White becomes black, yellow becomes
blue, etc. Use +negate to only negate the grayscale pixels of the image.
-noise radius +noise type
Add or reduce noise in an image. The principal function of noise peak
elimination filter is to smooth the objects within an image without losing
edge information and without creating undesired structures. The central idea
of the algorithm is to replace a pixel with its next neighbor in value
within a pixel window, if this pixel has been found to be noise. A pixel is
defined as noise if and only if this pixel is a maximum or minimum within
the pixel window.
Use -noise radius to specify the width of the neighborhood when reducing
noise.
Use +noise followed by a noise type to add noise to an image. Choose from
these noise types:
Gaussian Impulse Laplacian Multiplicative Poisson Random Uniform To print a
complete list of noises, use the -list noise option.
Also see the -evaluate noise functions that allos the use of a controlling
value to specify teh amount of noise that should be added to an image.
-normalize
Increase the contrast in an image by stretching the range of intensity
values. The intensity values are stretched to cover the entire range of
possible values. While doing so, black-out at most 2% of the pixels and
white-out at most 1% of the pixels.
Note that as of ImageMagick 6.4.7-0, -normalize is equivalent to
-contrast-stretch 2%x1%. (Before this version, it was equivalent to
-contrast-stretch 2%x99%).
All the channels are normalized in concert by the came amount so as to
preserve color integrity, when the default +channel setting is in use.
Specifing any other -channel setting will normalize the RGB channels
independently.
See -contrast-stretch for more details. Also see -auto-level for a 'perfect'
normalization that is better suited to mathematically generated images.
This operator is under review for re-development.
-ordered-dither threshold_map{,level...}
dither the image using a pre-defined ordered dither threshold map specified,
and a uniform color map with the given number of levels per color channel .
You can choose from these standard threshold maps:
threshold checks o2x2 o3x3 o4x4 o8x8 h4x4a h6x6a h8x8a h4x4o h6x6o h8x8o
h16x16o The 'o' maps are ordered diffused pixel threshold maps, while the
'h' maps are halftone threshold maps which are either 'a' angled, or 'o'
orthogonal. The 'checks' produce a 3 level checkerbord dither pattern. Or
you can define your own threshold map in a personal or system
"thresholds.xml" XML file.
To print a complete list of threshold, use the -list threshold option.
It is recommended that the +map operator be used after applying
-ordered-dither to reduce the number of colors an animated image sequence,
to less that 256 colors. This ensures that a common or global color table is
used when saving the result to a color limited file format such as GIF.
Note that at this time the exact same threshold dithering map is used for
all color channels, no attempt is made to offset or rotate the map for
different channels is made, to create an offset printing effect. (possible
future expansion)
-opaque color
change this color to the fill color within the image. The color argument is
defined using the format described under the -fill option. The -fuzz setting
can be used to match and replace colors similar to the one given.
The -transparent operator is exactly the same as -opaque but makes the
matching color transparent, rather than the same as the current -fill color.
Use +opaque to paint any pixel that does not match the target color.
-orient image orientation
specify orientation of a digital camera image. Choose from these
orientations:
bottom-left bottom-right left-bottom left-top right-bottom right-top
top-left top-right undefined To print a complete list of orientations, use
the -list orientation option.
-page geometry -page media[offset][{^!<>}] +page
Set the size and location of an image on the larger virtual canvas. See
Image Geometry for complete details about the geometry argument.
For convenience you can specify the page size using media (see below).
Offsets can then be added as with other geometry arguments (e.g. -page
Letter+43+43).
Use media as shorthand to specify the dimensions (widthxheight) of the
PostScript page in dots per inch or a TEXT page in pixels. The choices for a
PostScript page are:
media width height 11x17 792 1224 Ledger 1224 792
Legal 612 1008 Letter 612 792 LetterSmall 612 792
ArchE 2592 3456 ArchD 1728 2592 ArchC 1296 1728
ArchB 864 1296 ArchA 648 864 A0 2380 3368 A1
1684 2380 A2 1190 1684 A3 842 1190 A4 595 842
A4Small 595 842 A5 421 595 A6 297 421 A7 210
297 A8 148 210 A9 105 148 A10 74 105 B0 2836
4008 B1 2004 2836 B2 1418 2004 B3 1002 1418 B4
709 1002 B5 501 709 C0 2600 3677 C1 1837 2600
C2 1298 1837 C3 918 1298 C4 649 918 C5 459
649 C6 323 459 Flsa 612 936 Flse 612 936
HalfLetter 396 612 This option is also used to place subimages when
writing to a multi-image format that supports offsets, such as GIF89 and
MNG. When used for this purpose the offsets are always measured from the top
left corner of the canvas and are not affected by the -gravity option. To
position a GIF or MNG image, use -page{+-}x{+-}y (e.g. -page +100+200). When
writing to a MNG file, a -page option appearing ahead of the first image in
the sequence with nonzero width and height defines the width and height
values that are written in the MHDR chunk. Otherwise, the MNG width and
height are computed from the bounding box that contains all images in the
sequence. When writing a GIF89 file, only the bounding box method is used to
determine its dimensions.
For a PostScript page, the image is sized as in -geometry but positioned
relative to the lower left-hand corner of the page by {+-}xoffset{+-}y
offset. Use -page 612x792, for example, to center the image within the page.
If the image size exceeds the PostScript page, it is reduced to fit the
page. The default gravity for the -page option is NorthWest, i.e., positive
x and y offset are measured rightward and downward from the top left corner
of the page, unless the -gravity option is present with a value other than
NorthWest.
The default page dimensions for a TEXT image is 612x792.
This option is used in concert with -density.
Use +page to remove the page settings for an image.
-paint radius
simulate an oil painting. Each pixel is replaced by the most frequent color
in a circular neighborhood whose width is specified with radius.
-path path
write images to this path on disk. -pause seconds
Pause between animation loops. [animate] Pause for the specified number
of seconds before repeating the animation.
-pause seconds
Pause between snapshots. [import] Pause for the specified number of
seconds before taking the next snapshot.
-ping
efficiently determine image characteristics. -pointsize value
pointsize of the PostScript, OPTION1, or TrueType font. -polaroid angle
simulate a Polaroid picture. Use +polaroid to rotate the image at a random
angle between -15 and +15 degrees.
-posterize levels
reduce the image to a limited number of color levels. -precision value
set the maximum number of significant digits to be printed. -preview type
image preview type. Use this option to affect the preview operation of an
image (e.g. convert file.png -preview Gamma Preview:gamma.png). Choose from
these previews:
Rotate Shear Roll Hue Saturation Brightness Gamma Spiff Dull Grayscale
Quantize Despeckle ReduceNoise Add Noise Sharpen Blur Threshold EdgeDetect
Spread Shade Raise Segment Solarize Swirl Implode Wave OilPaint
CharcoalDrawing JPEG To print a complete list of previews, use the -list
preview option.
The default preview is JPEG.
-print string
interpret string and print to console. -process command
process the image with a custom image filter. The command arguments has the
form "module arg1 arg2 arg3 ... argN" where module is the name of the module
to invoke (e.g. "Analyze") and arg1 arg2 arg3 ... argN are an arbitrary
number of arguments to pass to the process module.
-profile filename +profile profile_name
Manage ICM, IPTC, or generic profiles in an image. Using -profile filename
adds an ICM (ICC color management), IPTC (newswire information), or a
generic profile to the image.
Use +profile profile_name to remove the indicated profile. ImageMagick uses
standard filename globbing, so wildcard expressions may be used to remove
more than one profile. Here we remove all profiles from the image except for
the XMP profile: +profile "!xmp,*".
Use identify -verbose to find out which profiles are in the image file. Use
-strip to remove all profiles (and comments).
To extract a profile, the -profile option is not used. Instead, simply write
the file to an image format such as APP1, 8BImageMagick, ICM, or IPTC.
For example, to extract the Exif data (which is stored in JPEG files in the
APP1 profile), use.
$magick> convert cockatoo.jpg profile.exif
It is important to note that results may depend on whether or not the
original image already has an included profile. Also, keep in mind that
-profile is an "operator" (as opposed to a "setting") and therefore a
conversion is made each time it is encountered, in order, in the
command-line. For instance, in the following example, if the original image
is CMYK with profile, a CMYK-CMYK-RGB conversion results.
$magick> convert CMYK.tif -profile "CMYK.icc" -profile "RGB.icc" RGB.tiff
Furthermore, since ICC profiles are not necessarily symmetric, extra
conversion steps can yield unwanted results. CMYK profiles are often very
asymmetric since they involve 3−>4 and 4−>3 channel mapping.
-quality value
JPEG/MIFF/PNG compression level. For the JPEG and MPEG image formats,
quality is 0 (lowest image quality and highest compression) to 100 (best
quality but least effective compression). The default is to use the estimate
quality of your input image otherwise 85. Use the -sampling-factor option to
specify the factors for chroma downsampling.
For the MIFF image format, quality/10 is the zlib compression level, which
is 0 (worst but fastest compression) to 9 (best but slowest). It has no
effect on the image appearance, since the compression is always lossless.
For the JPEG-2000 image format, quality is mapped using a non-linear
equation to the compression ratio required by the Jasper library. This
non-linear equation is intended to loosely approximate the quality provided
by the JPEG v1 format. The default quality value 85 results in a request for
16:1 compression. The quality value 100 results in a request for non-lossy
compression.
For the MNG and PNG image formats, the quality value sets the zlib
compression level (quality / 10) and filter-type (quality % 10). Compression
levels range from 0 (fastest compression) to 100 (best but slowest). For
compression level 0, the Huffman-only strategy is used, which is fastest but
not necessarily the worst compression.
If filter-type is 4 or less, the specified filter-type is used for all
scanlines:
0: none 1: sub 2: up 3: average 4: Paeth If filter-type is 5, adaptive
filtering is used when quality is greater than 50 and the image does not
have a color map, otherwise no filtering is used.
If filter-type is 6, adaptive filtering with minimum-sum-of-absolute-values
is used.
Only if the output is MNG, if filter-type is 7, the LOCO color
transformation and adaptive filtering with minimum-sum-of-absolute-values
are used.
The default is quality is 85, which means nearly the best compression with
adaptive filtering. The quality setting has no effect on the appearance of
PNG and MNG images, since the compression is always lossless.
For further information, see the PNG specification.
When writing a JNG image with transparency, two quality values are required,
one for the main image and one for the grayscale image that conveys the
alpha channel. These are written as a single integer equal to the main image
quality plus 1000 times the opacity quality. For example, if you want to use
quality 85 for the main image and quality 90 to compress the opacity data,
use -quality 90085.
-quantize colorspace
reduce colors in this colorspace. To print a complete list of colorspaces,
use the -list colorspace option.
-quiet
suppress all warning messages. Error messages are still reported.
-radial-blur angle
Blur around the center of the image. Note that this is actually a rotational
blur rather than a radial and as such actually mis-named.
The -virtual-pixel setting will determine how pixels which are outside the
image proper are blurred into the final result.
-raise thickness
Lighten or darken image edges. This will create a 3-D effect. Use -raise to
create a raised effect, otherwise use +raise.
Unlike the similar -frame option, -raise does not alter the dimensions of
the image.
-random-threshold lowxhigh
Apply a random threshold to the image. -recolor matrix
Translate, scale, shear, or rotate image colors. Although variable-sized
matrices can be used, typically one uses a 5x5 matrix for an RGBA image and
a 6x6 for CMYKA. Populate the last row with normalized values to translate.
The translation matrix is similar to that used by Adobe Flash except that
the offset is scaled to 1.0 (divide Flash offset by 255).
-red-primary x,y
Set the red chromaticity primary point. -regard-warnings
Pay attention to warning messages. -remap filename
Reduce the number of colors in an image to the colors used by this image. If
the -dither setting is enabled (the default) then the given colors are
dithered over the image as necessary, otherwise the closest color (in RGB
colorspace) is selected to replace that pixel in the image.
As a side effect of applying a -remap of colors across all images in the
current image sequence, all the images will have the same color table. That
means that when saved to a file format such as GIF, it will use that color
table as a single common or global color table, for all the images, without
requiring extra local color tables.
Use +remap to reduce all images in the current image sequence to use a
common color map over all the images. This equivalent to appending all the
images together (without extra background colors) and color reducing those
images using -colors with a 256 color limit, then -remap those colors over
the original list of images. This ensures all the images follow a single
color map.
If the number of colors over all the images is less than 256, then +remap
should not perform any color reduction or dithering, as no color changes are
needed. In that case, its only effect is to force the use of a global color
table. This recommended after using either -colors or -ordered-dither to
reduce the number of colors in an animated image sequence.
-region geometry
Set a region in which subsequent operations apply. The x and y offsets are
treated in the same manner as in -crop.
See Image Geometry for complete details about the geometry argument.
-remote
perform a remote operation. The only command recognized is the name of an
image file to load.
If you have more than one display application running simultaneously, use
the window option to specify which application to control.
-render
render vector operations. Use +render to turn off rendering vector
operations. This useful when saving the result to vector formats such as MVG
or SVG.
-repage geometry
Adjust the canvas and offset information of the image. This option is like
-page but acts as an image operator rather than a setting. You can
separately set the canvas size or the offset of the image on that canvas by
only providing those components.
See Image Geometry for complete details about the geometry argument.
If a ! flag is given the offset given is added to the existing offset to
move the image relative to its previous position. This useful for animation
sequences.
A given a canvas size of zero such as '0x0' forces it to recalculate the
canvas size so the image (at its current offset) will appear completely on
that canvas (unless it has a negative offset).
Use +repage to completely remove/reset the virtual canvas meta-data from the
images.
The -set 'page' option can be used to directly assign virtual canvas
meta-data.
-resample horizontalxvertical
Resample image to specified horizontal and vertical resolution. Resize the
image so that its rendered size remains the same as the original at the
specified target resolution. For example, if a 300 DPI image renders at 3
inches by 2 inches on a 300 DPI device, when the image has been resampled to
72 DPI, it will render at 3 inches by 2 inches on a 72 DPI device. Note that
only a small number of image formats (e.g. JPEG, PNG, and TIFF) are capable
of storing the image resolution. For formats which do not support an image
resolution, the original resolution of the image must be specified via
-density on the command line prior to specifying the resample resolution.
Note that Photoshop stores and obtains image resolution from a proprietary
embedded profile. If this profile exists in the image, then Photoshop will
continue to treat the image using its former resolution, ignoring the image
resolution specified in the standard file header.
-resize geometry
Resize an image. See Image Geometry for complete details about the geometry
argument. Offsets, if present in the geometry string, are ignored, and the
-gravity option has no effect.
If the -filter option precedes the -resize option, the image is resized with
the specified filter.
-respect-parentheses
settings remain in effect until parenthesis boundary. -reverse
Reverse the order of images in the current image list. -roll {+-}x{+-}y
roll an image vertically or horizontally by the amount given. A negative x
offset rolls the image left-to-right. A negative y offset rolls the image
top-to-bottom.
-rotate degrees{<}{>}
Apply Paeth image rotation (using shear operations) to the image. Use > to
rotate the image only if its width exceeds the height. < rotates the image
only if its width is less than the height. For example, if you specify
-rotate "-90>" and the image size is 480x640, the image is not rotated.
However, if the image is 640x480, it is rotated by -90 degrees. If you use >
or <, enclose it in quotation marks to prevent it from being misinterpreted
as a file redirection.
Empty triangles in the corners, left over from rotating the image, are
filled with the background color.
See also the -distort operator and specifically the 'ScaleRotateTranslate'
distort method.
-sample geometry
scale image using pixel sampling. -sample ignores the current -resize
-filter setting. The results are equivalent to using -resize with a -filter
setting of point, though -sample is a lot faster.
See Image Geometry for complete details about the geometry argument.
Offsets, if present in the geometry string, are ignored, and the -gravity
option has no effect.
-sampling-factor horizontal-factorxvertical-factor
sampling factors used by JPEG or MPEG-2 encoder and YUV decoder/encoder.
This option specifies the sampling factors to be used by the JPEG encoder
for chroma downsampling. If this option is omitted, the JPEG library will
use its own default values. When reading or writing the YUV format and when
writing the M2V (MPEG-2) format, use -sampling-factor 2x1 or
-sampling-factor 4:2:2 to specify the 4:2:2 downsampling method.
-scale geometry
scale the image. See Image Geometry for complete details about the geometry
argument. The -scale option uses a simpler, faster algorithm than -resize,
and it ignores the -filter setting if one is present. Offsets, if present in
the geometry string, are ignored, and the -gravity option has no effect.
-scene value
set scene number. This option sets the scene number of an image or the first
image in an image sequence.
-screen
specify the screen to capture. This option indicates that the GetImage
request used to obtain the image should be done on the root window, rather
than directly on the specified window. In this way, you can obtain pieces of
other windows that overlap the specified window, and more importantly, you
can capture menus or other popups that are independent windows but appear
over the specified window.
-seed
seed a new sequence of pseudo-random numbers -segment
cluster-thresholdxsmoothing-threshold
segment the colors of an image. Segment an image by analyzing the histograms
of the color components and identifying units that are homogeneous with the
fuzzy c-means technique. This is part of the ImageMagick color quantization
routines.
Specify cluster threshold as the number of pixels in each cluster that must
exceed the cluster threshold to be considered valid. Smoothing threshold
eliminates noise in the second derivative of the histogram. As the value is
increased, you can expect a smoother second derivative. The default is 1.5.
If the -verbose setting is defined, a detailed report of the color clusters
is returned.
-selective-blur geometry
Selectively blur pixels within a contrast threshold. -separate
separate an image channel into a grayscale image. Specify the channel with
-channel. -sepia-tone threshold
simulate a sepia-toned photo. Specify threshold as the percent threshold of
the intensity (0 - 99.9%).
This option applies a special effect to the image, similar to the effect
achieved in a photo darkroom by sepia toning. Threshold ranges from 0 to
QuantumRange and is a measure of the extent of the sepia toning. A threshold
of 80% is a good starting point for a reasonable tone.
-set attribute value
set an image attribute for all images in the current image sequence, after
they have been created or read in. Attributes of interest include -comment,
-delay, -dispose, and -page. For example:
$magick> convert rose: -set comment 'Rose is a rose is a rose is a rose'
rose.png $magick> identify -format %c rose.png Rose is a rose is a rose is a
rose
The -repage operator will also set the 'page' attribute of images already in
memory, but allows you to separately set the virtual canvas's size and
offset components, and also allows relative offset changes, and automatic
canvas size re-calculating. The above -set option is purely a direct,
unmodified assignment of the virtual canvas (page) meta-data.
Set image options by prefixing the value with option:. Set attributes of the
image registry by prefixing the value with registry:.
-shade azimuthxelevation
shade the image using a distant light source. Specify azimuth and elevation
as the position of the light source. Use +shade to return the shading
results as a grayscale image.
-shadow percent-opacity{xsigma}{+-}x{+-}y{%}
simulate an image shadow. -shared-memory
use shared memory. This option specifies whether the utility should attempt
to use shared memory for pixmaps. ImageMagick must be compiled with shared
memory support, and the display must support the MIT-SHM extension.
Otherwise, this option is ignored. The default is True.
-sharpen radius{xsigma}
sharpen the image. Use a Gaussian operator of the given radius and standard
deviation (sigma).
-shave geometry
Shave pixels from the image edges. The size portion of the geometry argument
specifies the width of the region to be removed from both sides of the image
and the height of the regions to be removed from top and bottom. Offsets are
ignored.
See Image Geometry for complete details about the geometry argument.
-shear Xdegrees[xYdegrees]
Shear the image along the x-axis and/or y-axis. The shear angles may be
positive, negative, or zero. When Ydegrees is omitted it defaults to 0. When
both angles are given, the horizontal component of the shear is performed
before the vertical component.
Shearing slides one edge of an image along the x-axis or y-axis (i.e.,
horizontally or vertically, respectively),creating a parallelogram. The
amount of each is controlled by the respective shear angle. For horizontal
shears, Xdegrees is measured clockwise relative to "up" (the negative
y-axis), sliding the top edge to the right when 0° convert logo: -shear 20x0 -shear 0x60 logo-sheared.png $magick>
convert logo: -shear 0x60 -shear 20x0 logo-sheared.png
The first of the two commands above is equivalent to the following, except
for the amount of empty space created; the command that follows generates a
smaller image, and so is a better choice in terms of time and space.
$magick> convert logo: -shear 20x60 logo-sheared.png
-sigmoidal-contrast contrastxmid-point
increase the contrast without saturating highlights or shadows. Increase the
contrast of the image using a sigmoidal transfer function without saturating
highlights or shadows. Contrast indicates how much to increase the contrast
(0 is none; 3 is typical; 20 is a lot); mid-point indicates where midtones
fall in the resultant image (0 is white; 50% is middle-gray; 100% is black).
By default the image contrast is increased, use +sigmoidal-contrast to
decrease the contrast.
-silent
operate silently. -size width[xheight][+offset]
set the width and height of the image. Use this option to specify the width
and height of raw images whose dimensions are unknown such as GRAY, RGB, or
CMYK. In addition to width and height, use -size with an offset to skip any
header information in the image or tell the number of colors in a MAP image
file, (e.g. -size 640x512+256).
For Photo CD images, choose from these sizes:
192x128 384x256 768x512 1536x1024 3072x2048 -sketch radius -sketch
radiusxsigma+angle
simulate a pencil sketch. Sketch with the given radius, standard deviation
(sigma), and angle. The angle given is the angle toward which the image is
sketched. That is the direction people would consider the object is coming
from.
-snaps value
Set the number of screen snapshots. [import] Use this option to grab more
than one image from the X server screen, to create an animation sequence.
-solarize threshold
negate all pixels above the threshold level. Specify factor as the percent
threshold of the intensity (0 - 99.9%).
This option produces a solarization effect seen when exposing a photographic
film to light during the development process.
-sparse-color method 'x,y color ...'
color the given image using the specified points of color, and filling the
other intervening colors using the given methods. Method Description
voronoi Simply map each pixel to the to nearest color point given. The
result are polygonal 'cells' of solid color. shepards Colors points
basied on the ratio of inverse distance squared. Generating spots of color
in a sea of the average of colors. barycentric three point triangle of
color given 3 points. Giving only 2 points will form a linear gradient
between those points. Gradient is however not restricted to just the
triangle or line. bilinear Like barycentric but for 4 points. Less than 4
points fall back to barycentric. The points are placed according to the
images location on the virtual canvas (-page or -repage offset), and do not
actually have to exist on the given image, but may be some point beyond the
edge of the image. All points are floating point values.
Only the color channels defined by the -channel are modified, whcih means
the matte/alpha transparency channel is not effected by default. If enabled,
the image also needs a the matte/alpha channel to be enabled for this
operator to effect an images transparency. This is typical transparency
handling for images.
All the above methods when given a single point of color will replace all
the colors in the image with the color given, regardless of the point. This
is logical, and provides an alternative technique to recolor a image to some
default value.
-splice geometry
Splice the current background color into the image. See Image Geometry for
complete details about the geometry argument. See -background to reset the
background color.
-spread amount
displace image pixels by a random amount. The argument amount defines the
size of the neighborhood around each pixel from which to choose a candidate
pixel to swap.
-stegano offset
hide watermark within an image. Use an offset to start the image hiding some
number of pixels from the beginning of the image. Note this offset and the
image size. You will need this information to recover the steganographic
image (e.g. display -size 320x256+35 stegano:image.png).
-stereo +x{+y}
composite two images to create a stereo anaglyph. [composite] The left
side of the stereo pair is saved as the red channel of the output image. The
right side is saved as the green channel. Red-green stereo glasses are
required to properly view the stereo image.
-storage-type type
pixel storage type. Here are the valid types: char store pixels as
unsigned characters double store pixels as doubles float store
pixels as floats integer store pixels as integers long store
pixels as longs quantum store pixels in the native depth of your
ImageMagick distribution short store pixels as unsigned shorts Float
and double types are normalized from 0.0 to 1.0 otherwise the pixels values
range from 0 to the maximum value the storage type can support.
-stretch fontStretch
Set a type of stretch style for fonts. This setting suggests a type of
stretch that ImageMagick should try to apply to the currently selected font
family. Select fontStretch from the following.
Any Condensed Expanded ExtraCondensed ExtraExpanded Normal SemiCondensed
SemiExpanded UltraCondensed UltraExpanded To print a complete list of
stretch types, use -list stretch.
For other settings that affect fonts, see the options -font, -family,
-style, and -weight.
-strip
strip the image of any profiles or comments. -stroke color
color to use when stroking a graphic primitive. The color is specified using
the format described under the -fill option.
See -draw for further details.
-strokewidth value
set the stroke width. See -draw for further details.
-style fontStyle
Set a font style for text. This setting suggests a font style that
ImageMagick should try to apply to the currently selected font family.
Select fontStyle from the following.
Any Italic Normal Oblique For other settings that affect fonts, see the
options -font, -family, -stretch, and -weight.
-swap index,index
Swap the positions of two images in the image sequence. For example, -swap
0,2 swaps the first and the third images in the current image sequence. Use
+swap to switch the last two images in the sequence.
-swirl degrees
swirl image pixels about the center. Degrees defines the tightness of the
swirl.
-taint
Mark the image as modified even if it isn't. -text-font name
font for writing fixed-width text. Specifies the name of the preferred font
to use in fixed (typewriter style) formatted text. The default is 14 point
Courier.
You can tag a font to specify whether it is a PostScript, TrueType, or
OPTION1 font. For example, Courier.ttf is a TrueType font and x:fixed is
OPTION1.
-texture filename
name of texture to tile onto the image background. -threshold value{%}
Apply simultaneous black/white threshold to the image. Any pixel values
(more specifically, those channels set using ‑channel) that exceed the
specified threshold are reassigned the maximum channel value, while all
other values are assigned the minimum.
The threshold value can be given as a percentage or as an absolute integer
value corresponding to the desired channel value. When given as an integer,
the minimum attainable value is 0 (corresponding to black when all channels
are affected), but the maximum value (corresponding to white) is that of the
quantum depth of the particular build of ImageMagick, and is therefore
dependent on the installation. For that reason, a reasonable recommendation
for most applications is to specify the threshold values as a percentage.
The following would force pixels with red values above 50% to have 100% red
values, while those at or below 50% red would be set to 0 in the red
channel. The green, blue, and alpha channels (if present) would be
unchanged.
$magick> convert in.png -channel red -threshold 50% out.png
As (possibly) impractical but instructive examples, the following would
generate an all-black and an all-white image with the same dimensions as the
input image.
$magick> convert in.png -threshold 100% black.png $magick> convert in.png
-threshold -1 white.png
Note that the values of the transparency channel is treated as 'matte'
values (0 is opaque) and not as 'alpha' values (0 is transparent).
See also ‑black‑threshold and ‑white‑threshold.
-thumbnail geometry
Create a thumbnail of the image. This is similar to -resize, except it is
optimized for speed and any image profile, other than a color profile, is
removed to reduce the thumbnail size. To strip the color profiles as well,
add -strip just before of after this option.
See Image Geometry for complete details about the geometry argument.
-tile filename
Set the tile image used for filling a subsequent graphic primitive. -tile
geometry
Specify the layout of images . [montage] See Image Geometry for complete
details about the geometry argument.
-tile
Specifies that a subsequent composite operation is repeated across and down
image. [composite] -tile-offset {+-}x{+-}y
Specify the offset for tile images, relative to the background image it is
tiled on. This should be set before the tiling image is set by -tile or
-texture, or directly applied for creating a tiled canvas using TILE: or
PATTERN: input formats.
Internally ImageMagick does a -roll of the tile image by the arguments given
when the tile image is set.
-tint value
Tint the image with the fill color. Tint the image with the fill color.
Specify the amount of tinting as a percentage. Pure colors like black, white
red, yellow, will not be affected by -tint. Only mid-range colors such as
the various shades of grey.
-title string
Assign a title to displayed image. [animate, display, montage] Use this
option to assign a specific title to the image. This assigned to the image
window and is typically displayed in the window title bar. Optionally you
can include the image filename, type, width, height, Exif data, or other
image attribute by embedding special format characters described under the
-format option.
For example,
-title "%m:%f %wx%h"
produces an image title of MIFF:bird.miff 512x480 for an image titled
bird.miff and whose width is 512 and height is 480.
-transform
transform the image. This option applies the transformation matrix from a
previous -affine option.
$magick> convert -affine 2,2,-2,2,0,0 -transform bird.ppm bird.jpg
-transparent color
Make this color transparent within the image. The color argument is defined
using the format described under the -fill option. The -fuzz setting can be
used to match and replace colors similar to the one given.
The -opaque operator is exactly the same as -transparent but replaces the
matching color same as the current -fill color setting.
This does not define the 'transparency color' used for color-mapped image
formats, such as GIF. For that use -transparent-color
Use +opaque to invert the pixels matched, that is paint any pixel that does
not match the target color, with the fill color.
-transparent-color color
Set the transparent color. Sometimes this is used for saving to image
formats such as GIF and PNG8 which uses this color to represent boolean
transparency. This does not make a color transparent, it only defines what
color the transparent color is in the color palette of the saved image. Use
-transparent to make an opaque color transparent.
This option allows you to have both an opaque visible color, as well as a
transparent color of the same color value without conflict. That is, you can
use the same color for both the transparent and opaque color areas within an
image. This, in turn, frees to you to select a transparent color that is
appropriate when an image is displayed by an application that does not
handle a transparent color index, while allowing ImageMagick to correctly
handle images of this type.
The default transparent color is #00000000, which is fully transparent
black.
-transpose
Mirror the image along the top-left to bottom-right diagonal. This option
mathematically transposes the pixel array. It is equivalent to the sequence
-flip -rotate 90.
-transverse
Mirror the image along the images bottom-left top-right diagonal. Equivalent
to the operations -flop -rotate 90. -treedepth value
tree depth for the color reduction algorithm. Normally, this integer value
is zero or one. A value of zero or one causes the use of an optimal tree
depth for the color reduction algorithm.
An optimal depth generally allows the best representation of the source
image with the fastest computational speed and the least amount of memory.
However, the default depth is inappropriate for some images. To assure the
best representation, try values between 2 and 8 for this parameter. Refer to
the color reduction algorithm for more details.
The -colors or -monochrome option, or writing to an image format which
requires color reduction, is required for this option to take effect.
-trim
trim an image. This option removes any edges that are exactly the same color
as the corner pixels. Use -fuzz to make -trim remove edges that are nearly
the same color as the corner pixels.
The page or virtual canvas information of the image is preserved allowing
you to extract the result of the -trim operation from the image. Use a
+repage to remove the virtual canvas page information if it is unwanted.
If the trimmed image 'disappears' an warning is produced, and a special
single pixel transparent 'missed' image is returned, in the same way as when
a -crop operation 'misses' the image proper.
-type type
the image type. Choose from: Bilevel, Grayscale, GrayscaleMatte, Palette,
PaletteMatte, TrueColor, TrueColorMatte, ColorSeparation,
ColorSeparationMatte, or Optimize.
Normally, when a format supports different subformats such as grayscale and
truecolor, the encoder will try to choose an efficient subformat. The -type
option can be used to overrride this behavior. For example, to prevent a
JPEG from being written in grayscale format even though only gray pixels are
present, use.
$magick> convert bird.png -type TrueColor bird.jpg
Similarly, use -type TrueColorMatte to force the encoder to write an alpha
channel even though the image is opaque, if the output format supports
transparency.
Use -type optimize to ensure the image is written in the smallest possible
file size.
-undercolor color
set the color of the annotation bounding box. The color is specified using
the format described under the -fill option.
See -draw for further details.
-update seconds
detect when image file is modified and redisplay. Suppose that while you are
displaying an image the file that is currently displayed is over-written.
display will automagically detect that the input file has been changed and
update the displayed image accordingly.
-unique-colors
discard all but one of any pixel color. -units type
the units of image resolution. Choose from: Undefined, PixelsPerInch, or
PixelsPerCentimeter. This option is normally used in conjunction with the
-density option.
-unsharp radius -unsharp radiusxsigma{+amount}{+threshold}
sharpen the image with an unsharp mask operator. The -unsharp option
sharpens an image. The image is convolved with a Gaussian operator of the
given radius and standard deviation (sigma). For reasonable results, radius
should be larger than sigma. Use a radius of 0 to have the method select a
suitable radius.
The parameters are:
radius: The radius of the Gaussian, in pixels, not counting the center
pixel (default 0). sigma: The standard deviation of the Gaussian, in
pixels (default 1.0). amount: The fraction of the difference between the
original and the blur image that is added back into the original (default
1.0). threshold: The threshold, as a fraction of QuantumRange, needed to
apply the difference amount (default 0.05). -verbose
print detailed information about the image when this option preceds the
-identify option or info:. -version
print ImageMagick version string and exit. -view string
FlashPix viewing parameters. -vignette radius{xsigma}{+-}x{+-}y{%}
soften the edges of the image in vignette style. -virtual-pixel method
Specify contents of virtual pixels. This option defines what color source
should be used if and when a color lookup completely 'misses' the source
image. The color(s) that appear to surround the source image. Generally this
color is derived from the source image, but could also be set to a specify
background color.
Choose from these methods:
background: the area surrounding the image is the background color
black: the area surrounding the image is black checker-tile:
alternate squares with image and background color dither:
non-random 32x32 dithered pattern edge: extend the edge
pixel toward infinity gray: the area surrounding the image
is gray horizontal-tile: horizontally tile the image, background color
above/below horizontal-tile-edge: horizontally tile the image and replicate
the side edge pixels mirror: mirror tile the image random:
choose a random pixel from the image tile: tile
the image (default) transparent: the area surrounding the image is
transparent blackness vertical-tile: vertically tile the image, sides
are background color vertical-tile-edge: vertically tile the image and
replicate the side edge pixels white: the area surrounding
the image is white The default value is "edge".
This most important for distortion operators such as -distort, -implode, and
-fx. However it also effects operations that may access pixels just outside
the image proper, such as -convolve, -blur, and -sharpen.
To print a complete list of virtual pixel types, use the -list virtual-pixel
option.
-visual type
Animate images using this X visual type. [animate, display] Choose from
these visual classes:
StaticGray GrayScale StaticColor PseudoColor TrueColor DirectColor default
visual id The X server must support the visual you choose, otherwise an
error occurs. If a visual is not specified, the visual class that can
display the most simultaneous colors on the default screen is chosen.
-watermark brightnessxsaturation
Watermark an image using the given percentages of brightness and
saturation. [composite] Take a grayscale image (with alpha mask) and
modify the destination image's brightness according to watermark image's
grayscale value and the brightness percentage. The destinations color
saturation attribute is just direct modified by the saturation percentage,
which defaults to 100 percent (no color change).
-wave amplitude -wave amplitudexwavelength
Shear the columns of an image into a sine wave. Specify amplitude and
wavelength of the wave.
-weight fontWeight
Set a font weight for text. This setting suggests a font weight that
ImageMagick should try to apply to the currently selected font family. Use a
positive integer for fontWeight or select from the following.
fontWeight Description All No effect. Bold Same as fontWeight =
700. Bolder Add 100 to font weight if currently ≤ 800.
Lighter Subtract 100 to font weight if currently ≤ 100. Normal Same as
fontWeight = 400. To print a complete list of weight types, use -list
weight.
For other settings that affect fonts, see the options -font, -family,
-stretch, and -style.
-white-point x,y
chromaticity white point. -white-threshold value{%}
Force to white all pixels above the threshold while leaving all pixels at or
below the threshold unchanged. The threshold value can be given as a
percentage or as an absolute integer value within [0, QuantumRange]
corresponding to the desired ‑channel value. See ‑threshold for more details
on thresholds and resulting values.
-window id
Make the image the background of a window. [animate, display] id can be a
window id or name. Specify root to select X's root window as the target
window.
By default the image is tiled onto the background of the target window. If
backdrop or -resize are specified, the image is surrounded by the background
color. Refer to X RESOURCES for details.
The image will not display on the root window if the image has more unique
colors than the target window colormap allows. Use -colors to reduce the
number of colors.
-window-group
specify the window group. -write filename
write an image sequence. The image sequence preceding the -write filename
option is written out, and processing continues with the same image in its
current state if there are additional options. To restore the image to its
original state after writing it, use the +write filename option.
Use -compress to specify the type of image compression.