diff images from the command line
Important business programmers don't have time to switch away from their terminal to view the diff of an image they're about to commit. The three seconds it takes to open an external diff visualization program could drive your sales team to drink and make inappropriate remarks to your new employees. Increase your productivity bottom line today, with spaceman-diff!
spaceman-diff is a quick drop in to git-diff. The idea is that you can just git diff like normal and, if you've changed an image file, spaceman-diff will render your images in a colorful ASCII approximation in your shell along with helpful data like file size changes.
Here's a quick example of what you might see:
The goal is that spaceman-diff gives you a quick way of verifying that yes, the image you're committing is the image you want to commit, and yes, the image you're committing isn't accidentally 20 terabytes in size or something foolish like that.
Note: right now, spaceman-diff requires a change in the image; you won't see a diff rendered if you're simply adding or removing a file to your repo. git diff apparently doesn't pass things through to spaceman-diff at all in this case. There's probably a way to handle this, so pull requests accepted.
There are two dependencies that you need before you can fiddle with pixels and characters and junk: jp2a and ImageMagick. jp2a handles conversion of a JPEG to ASCII, and ImageMagick can do everything from image conversion to probably running a nuclear reactor.
If you're using Homebrew, blindly run this:
brew install jp2a imagemagick
If you're using apt, you should be able to install your dependencies in a similar manner:
sudo apt-get install jp2a imagemagick
Once you have your dependencies installed, drop spaceman-diff onto your system or your dotfiles directory or whatever kooky stuff you're using. If you're using Homebrew, you can instead install spaceman-diff with brew install spaceman-diff. After that, you need to configure Git to use spaceman-diff for all your image diffs.
If you don't have one already, create a file at ~/.config/git/attributes and add this to it:
*.png diff=spaceman-diff
*.jpg diff=spaceman-diff
*.jpeg diff=spaceman-diff
*.gif diff=spaceman-diffThis basically tells Git to use the spaceman-diff strategy to render the diff for these four particular file extensions.
Next, you need to tell Git about spaceman-diff. Do that by editing ~/.gitconfig:
[diff "spaceman-diff"]
command = /path/to/spaceman-diffAt this point, you should be ready to go. Try it out on a directory with an unstaged image change and run it with git diff.
Send a pull request with your changes, and make sure the tests pass. You can run dem tests with ./tests in your working directory.
This was cobbled together by @holman.