This has less practical value that I'd like to admit but I decided to go down the rabit hole of trying to figure out how to create simple GUI for a bash script. This script takes a retina image and down converts into into a plethora of formats. Perhaps one day this could be wedged into a very simple xcode project that gives it a real GUI and thus more options. I simply ported my CodeKit 3 hook to an independent shell script, and added Zenity after exploring a few options. Notably there is no error catching.

Dependancies

    brew install imagemagick --with-openjpeg
    brew install webp
    brew install mozjpeg
    brew install zenity
  

GitHub Jist