Q:

Ignoring differences in brightness with ImageMagick compare tool

I'm using compare to find if something has changed between two photos. It generally works well, except when the room suddenly becomes a bit darker or brighter. So I'm wondering - is it possible to ignore the difference in brightness when running compare?
So far I'm using the command below:
compare -fuzz 15% -metric ae /path/to/image1.jpg /path/to/image2.jpg /path/to/diff.png

For example, for this set of images, I would get approximately 5% difference, while I would like to bring it below 1% or even less if possible.

Any suggestion?

A:

You could normalize the two images, then compare those:
convert VaoZF.jpg -normalize image1.ppm
convert whgkn.jpg -normalize image2.ppm
compare -fuzz 15% -metric ae image1.ppm image2.ppm diff.png

You can get the difference metric with a single command and without making any temporary files:
magick \( VaoZF.jpg -normalize \) \( whgkn.jpg -normalize \) \
      -fuzz 15% -metric ae -compare -format "%[distortion]" info:

If you are on Windows, use "(" and ")" instead of "\(" and "\)" and use a "^" instead of a "\" for suppressing the line break, and replace "%" with "%%".

