This is a hack to display pixel-by-pixel differences between 2 images, typically registered.
ImageMagick offers an example image differencing invocation:
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magick composite img1.jpg img2.jpg -compose difference diff.jpg
- small differences are nearly black, displaying poorly
- differences are also absolute; gray - blue == blue - gray
This invocation results in middle gray for no difference, with gray - blue = yellow:
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magick CZP_Helicon_Comparison_H.jpg.crdownload CZP_Helicon_Comparison_C.jpg.crdownload -compose Mathematics -define compose:args="0,-1,1,.5" -composite ugoo.jpg
and resulting ugoo.jpg is this: Documentation for ImageMagick Composition Mathematics:
https://imagemagick.org/Usage/compose/#mathematics
Pretending neither to type reliably nor remember that syntax,
I hacked an dimg shell script that expects 3 filenames
and created an alias for invoking it.
https://blekenbleu.github.io/ImageProcessing/dimg.html
A next step involves hacking a utility to register image pairs,
given images of mismatched magnifications and/or orientations.