git-diff-image

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.

Platforms

Only macOS and Linux at the moment. Patches welcome!

Examples

$ 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.

Installation

1. Install exiftool and either ImageMagick or GraphicsMagick with the ImageMagick compatibility links. (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 (new versions):

   sudo apt install exiftool imagemagick xdg-utils

   Debian / Ubuntu (older versions):

   sudo apt install exiftool imagemagick xdg-open

   Debian / Ubuntu (if using GraphicsMagick):

   sudo apt install exiftool graphicsmagick graphicsmagick-imagemagick-compat xdg-utils

   Arch Linux:

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

   openSUSE Tumbleweed:

   sudo zypper install exiftool ImageMagick xdg-utils bc

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'

Git LFS

If you are using Git LFS then you have some extra manual configuration. This has been left as a manual step because you need to choose whether to do this on a per-repository basis or set it in your global configuration.

Instead of the default configuration in ~/.gitattributes which looks like this:

*.png diff=image

You need to extend it to look something like this:

*.png filter=lfs diff=lfs diff=image merge=lfs -text

You can either do this in your ~/.gitattributes or a .gitattributes file at the root of each repository.

Public domain dedication

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/.