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

2COLORTHRESH


Automatically thresholds an image to binary (b/w) format using an adaptive spatial subdivision color reduction technique.

Download Script

last modified: October 06, 2014



USAGE: 2colorthresh infile outfile
USAGE: 2colorthresh [-help]

There are no options

PURPOSE: To automatically thresholds an image to binary (b/w) format using an adaptive spatial subdivision color reduction technique.

DESCRIPTION: 2COLORTHRESH automatically thresholds an image to binary (b/w) format using an adaptive spatial subdivision color reduction technique. This is the -colors IM operator as implemented with slight modification from Anthony's Examples at http://www.imagemagick.org/Usage/quantize/#two_color For algorithm details, see http://www.imagemagick.org/script/quantize.php

ARGUMENTS:

NOTE: It is highly recommended that the output not be specified as a JPG image as that will cause compression and potentially a non-binary (i.e. a graylevel) result. GIF is the recommended output format.

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


2Color Thresholding Of Various Images

Pictures Were Obtained from:
blood.jpg from http://www.istanbul.edu.tr/eng/ee/jeee/main/pages/issues/is62/62008.pdf
fingerprint.jpg from http://www.istanbul.edu.tr/eng/ee/jeee/main/pages/issues/is62/62008.pdf
flower.jpg from http://www.jhlabs.com/ip/blurring.html
house.jpg from http://en.wikipedia.org/wiki/Otsu's_method
kanji.jpg from http://www.measurement.sk/2004/S1/Yong.pdf
parts.gif from http://www.ph.tn.tudelft.nl/Courses/FIP/noframes/fip-Segmenta.html
rice.jpg from http://www.istanbul.edu.tr/eng/ee/jeee/main/pages/issues/is62/62008.pdf
tank.jpg from http://stinet.dtic.mil/cgi-bin/GetTRDoc?AD=ADA464347&Location=U2&doc=GetTRDoc.pdf
textsample.jpg from http://signal.ece.utexas.edu/seminars/dsp_seminars/01fall/211_seeger_mf.pdf
lena2g_edge1.jpg was created using the IM function -edge 1

Original Image

Thresholded Image



See A Comparison Of Each Image Against Each Thresholding Technique



What the script does is as follows:

  • Disables dithering
  • Selects 2 colors for the IM function -colors
  • Converts to grayscale
  • Stretches the images so that the minimum value goes to black
    and the maximum value goes to white

This is equivalent to the following IM commands

  • convert $infile +dither -colors 2 -colorspace gray -contrast-stretch 0 $outfile