dimg: visual image difference utility

visualizing differences betweeen images

What

Usefully display differences between similar image pairs:

ball.png	ballsp4a.png
magick composite ball.png ballsp4a.png -compose difference diff.png diff.png	magick ball.png ballsp4a.png -compose Mathematics -define compose:args='0,1,-1,.5' -composite dimg.png dimg.png

Several image utilities, including ImageMagick, offer an image difference generation option,
with smaller difference nearer black (e.g. diff.png)
and all differences absolute, e.g.: red-green == green-red.
However, displayed differences are more visible near middle gray (e.g. dimg.png).
ImageMagick's User Defined Mathematical Compose Method supports this more useful alternative.
Differences would ideally be calculated in a more nearly perceptual color space, e.g. CIELab.

@echo off
: generate a difference image (third argument) from (first 2 argument) images
echo magick %1 %2 -compose Mathematics -define compose:args="0,-1,1,.5" -composite %3
magick %1 %2 -compose Mathematics -define compose:args="0,-1,1,.5" -composite %3