This is an extension to 'git diff' that provides support for diffing images. It can also be run as a direct CLI command for diffing two image files.

Only macOS and Linux at the moment. Patches welcome!

$ git diff
--- a/anImageThatHasChanged.jpg
+++ b/anImageThatHasChanged.jpg
@@ -1,5 +1,5 @@
 ExifTool Version Number         : 9.76
-File Size                       : 133 kB
+File Size                       : 54 kB
 File Access Date/Time           : 2015:05:02 20:01:21-07:00
 File Type                       : JPEG
 MIME Type                       : image/jpeg

$ git diff-image
# The same output as above, *and* a montage of the visual differences will be
# generated and opened in Preview.

$ diff-image anImageThatHasChanged1.jpg anImageThatHasChanged2.jpg
# The same as above, only using files on disk not git differences.

1. Install exiftool and ImageMagick. (The script will cope with these missing, but it's not going to be very exciting without them).

   macOS:

   brew install exiftool imagemagick

   Debian / Ubuntu:

   sudo apt install exiftool imagemagick xdg-open

   Arch Linux:

   pacman -S xdg-utils perl-image-exiftool imagemagick

2. Run ./install.sh, which will configure your global git config for you. It will tell you what it's done, so it should look something like this:

~/git-diff-image $ ./install.sh
+ git config --global core.attributesfile '~/.gitattributes'
+ touch '/Users/yourname/.gitattributes'
+ echo '*.gif diff=image' >>'/Users/yourname/.gitattributes'
+ echo '*.jpeg diff=image' >>'/Users/yourname/.gitattributes'
+ echo '*.jpg diff=image' >>'/Users/yourname/.gitattributes'
+ echo '*.png diff=image' >>'/Users/yourname/.gitattributes'
+ git config --global alias.diff-image '!f() { cd -- "${GIT_PREFIX:-.}"; GIT_DIFF_IMAGE_ENABLED=1 git diff "$@"; }; f'
+ git config --global diff.image.command '~/git-diff-image/git_diff_image'

The files in this repository are by Ewan Mellor, and are dedicated to the public domain. To the extent possible under law, Ewan Mellor has waived all copyright and related or neighboring rights to this work. http://creativecommons.org/publicdomain/zero/1.0/.