Fred's ImageMagick Scripts



    Licensing:

    Copyright © Fred Weinhaus

    My scripts are available free of charge for non-commercial use, ONLY.

    For use of my scripts in commercial (for-profit) environments or non-free applications, please contact me (Fred Weinhaus) for licensing arrangements. My email address is fmw at alink dot net.

    If you: 1) redistribute, 2) incorporate any of these scripts into other free applications or 3) reprogram them in another scripting language, then you must contact me for permission, especially if the result might be used in a commercial or for-profit environment.

    Usage, whether stated or not in the script, is restricted to the above licensing arrangements. It is also subject, in a subordinate manner, to the ImageMagick license, which can be found at: http://www.imagemagick.org/script/license.php

REMAP


Remaps the colors in an image using a 3D color distance metric relative to a color table map image.

Download Script

last modified: September 26, 2017



USAGE: remap [-n numcolors ] [-m metric] [-s] infile mapfile outfile
USAGE: remap [-h or -help]

-n ... numcolors .... desired number of colors, if the input image
..................... has more than 256 unique colors;
..................... 0<integer<=256; default is to use the number
..................... of input colors if <= 256, otherwise 24
-m ... metric ....... colorspace distance metric; choices are:
..................... RGB or RGBL (luminance weighted RGB);
..................... default=RGB
-s .................. show/display textual data to the terminal

PURPOSE: To remap the colors in an image using a 3D color distance metric relative to a color table map image.

DESCRIPTION: REMAP remaps colors in an image using a 3D color distance metric relative to a (map) color table image. The mapfile is an image that contains only the desired output colors. The infile should contain a limited number of colors, less than or equal to 256. However, it may take a long time to process with 256 colors and generally will not more produce results much different than much fewer colors, certainly no more colors than are in the mapfile.

The RGB distance metric is dist=sqrt(rdiff^2+gdiff^2+bdiff^2), where the diffs are the channel differences between the infile color and the mapfile color.

The RGBL distance metric is dist=sqrt((0.299*rdiff^2+0.587gdiff^2+0.114*bdiff^2)*0.75+ldiff^2)), where ldiff is the difference in Rec601 luminosity value between the infile color and the mapfile color, with lum=(0.299*R+0.587G+0.114*B).

ARGUMENTS:

-n numcolors ... NUMCOLORs is the desired number of colors. If the input image has more than 256 unique colors, then the image will use -colors numcolors to reduce the number of colors. Values are 0<integer<=256. The default is to use the number of input colors, if it is less than or equal to 256, otherwise 24.

-m metric ... METRIC is the colorspace distance metric. The choices are: RGB or RGBL (luminance weighted RGB). The default=RGB

-s ... SHOW/display textual data to the terminal

References:
http://bisqwit.iki.fi/story/howto/dither/jy/
http://en.wikipedia.org/wiki/X11_color_names
http://www.imagemagick.org/discourse-server/viewtopic.php?f=3&t=19646#p77472

Limitation: The script only works for fully opaque images and map images.

CAVEAT: No guarantee that this script will work on all platforms, nor that trapping of inconsistent parameters is complete and foolproof. Use At Your Own Risk.


EXAMPLES

Original

Map Image
(http://en.wikipedia.org/wiki/X11_color_names)

Arguments:
-n 12 -m RGB

Arguments:
-n 12 -m RGBL

Arguments:
-n 24 -m RGB

Arguments:
-n 24 -m RGBL

Arguments:
-n 50 -m RGB

Arguments:
-n 50 -m RGBL



What the script does is as follows:

  • Gets the array of colors from the map file
  • Processed the image with -color ncolors if the image has
    more than 256 colors
  • Gets the array of colors from the (reduced color) image file
  • For each color in the image, finds the matching color in
    the mapfile using the smallest distance from the distance metric
  • Processes the image using the pairs of colors to remap the image

This is equivalent to the following IM commands for metric=RGB:

  • convert -quiet -regard-warnings "$infile" -alpha off +repage -colorspace RGB -depth 8 "$dir/tmpA.mpc"
  • convert -quiet -regard-warnings "$mapfile" -alpha off -depth 8 -colorspace RGB +repage "$dir/tmpM.mpc"
  • OLDIFS=$IFS
  • mapcolorArr=(`convert $dir/tmpM.mpc -alpha off -depth 8 -format %c histogram:info:- | \
    sed -n 's/^.*: *[(]\(.*\)[)].*#.*$/\1/p' | sed 's/ *//g'`)
  • convert $dir/tmpA.mpc +dither -colors $ncolors -depth 8 $dir/tmpA.mpc
  • colorArr=(`convert $dir/tmpA.mpc -alpha off -depth 8 -format %c histogram:info:- | \
    sed -n 's/^.*: *[(]\(.*\)[)].*#.*$/\1/p' | sed 's/ *//g'`)
  • colorlist=":${colorArr[*]}:${mapcolorArr[*]}:"
  • IFS=":"
  • pairlist=`for color in $colorlist; do
    echo "$color"
    done |\
    awk ' { FS="x"; j=NR; Arr[j]=$1; split(Arr[2], colorArr, " "); split(Arr[3], mapcolorArr, " "); }
    END { FS=" ";
    for (j in colorArr)
    { mindist=1000000; k=1; for (i in mapcolorArr)
    { split(colorArr[j], c, ","); split(mapcolorArr[i], m, ",");
    dist=sqrt( (c[1]-m[1])*(c[1]-m[1])+(c[2]-m[2])*(c[2]-m[2])+(c[3]-m[3])*(c[3]-m[3]) );
    if ( dist<mindist) { mindist=dist; k=i; cc="rgb("c[1]","c[2]","c[3]")"; mm="rgb("m[1]","m[2]","m[3]")"; } } print cc":"mm; }
    } '`
  • IFS=$OLDIFS
  • pairArr=($pairlist)
  • dim=`convert $dir/tmpA.mpc -format "%wx%h" info:`
  • convert -size $dim xc:none -depth 8 $dir/tmpO.mpc
  • i=1
  • for colorpair in ${pairArr[*]}; do
    color1=`echo "$colorpair" | cut -d: -f1`
    color2=`echo "$colorpair" | cut -d: -f2`
    convert \( $dir/tmpA.mpc \
    +transparent "$color1" \
    -fill "$color2" -opaque "$color1" \) $dir/tmpO.mpc \
    -composite $dir/tmpO.mpc
    i=`expr $i + 1`
    done
  • convert $dir/tmpO.mpc $outfile