Update: With the assets command of the TiCons CLI / Module this can be done even simpeler by calling $ ticons assets or an alloy.ymk using:

With all these different pixel densities, you can spend a good deal of time resizing images. For iOS, this means downsizing your retina @2x images by 50%. I wrote a little NodeJS script to use in an alloy.jmk or Alloy Build Configuration File that automatically generates non-retina images by using ImageMagick on new and changed retina ones.

Get the script at Github:
https://gist.github.com/FokkeZB/6095822

How to use

1. Open terminal
2. Install Homebrew
   ruby -e "$(curl -fsSL https://raw.github.com/Homebrew/homebrew/go/install)"
3. Install ImageMagick
   brew install imagemagick
4. Install the ImageMagick NodeJS module
   sudo npm install -g imagemagick
5. Copy the alloy.jmk to your Alloy project or add the unRetina function to the pre:compile hook of your existing alloy.jmk file:
   
   1 2 3 4

   task("pre:load", function(event, logger) {   unRetina(event, logger);   // other stuff you have });

6. Never care about non-retina files again!