Cookbook.md

@@ -5,6 +5,10 @@
 * translate mp3 to ogg: `ffmpeg -i file.mp3 file.ogg`
 
 * pngcrush everything: `for file in **/*.png ; do pngcrush -brute -ow $file; done`
+* pngcrush everything that's changed:
+```shell
+for file in $(git status --porcelain --untracked=all | cut -b 4- | grep "\.png$") ; do pngcrush -brute -ow $file; done
+```
 
 * sizes of things in C#:
 ```