Automatically resizes images labeled at Retina sizes to lower resolutions. Plop an @2x image into an images folder, and get the normal version too. This must be used with the Brunch build tool.

retina-brunch is designed to be an npm package for use with the build tool Brunch. To install this as a dependency for your Brunch repository, run npm install --save retina-brunch, which will add a line to your package.json file.

By default, retina-brunch looks in the images directory in the public folder (the output folder) specified in your Brunch configuration. It then collects all the Retina files matching the regular expression /(@2[xX])\.(?:gif|jpeg|jpg|png)$/ and creates normal versions by halving the height and width and depositing the file in the same directory as the original.

retina-brunch can be customized by adding retina to the plugins section of your config.coffee.

exports.config =
  plugins:
    retina:
      regexp: /(@2[xX])\.(?:gif|jpeg|jpg|png)$/
      path: 'images'
      minWidth: 0
      minHeight: 0
      assetsPath: 'public' # could be set to i.e. './app/assets'

• RegExp regexp takes a Coffeescript/Javascript regular expression with exactly one group (if you specify more, they will be ignored; if you specify fewer, it will break) specifying the string that distinguishes a Retina file from a normal file. By convention, this is normally @2x or @2X. The name of the normal file will be determined by removing this group. The image resizing tool does not support image formats other than those already specified.
• String path is the path to your images folder within the public folder specified in config.coffee, or any directory you want to monitor for files matching the Retina regular expresssion.
• Integer minHeight and minWidth filter the files which are processed. In particular, a file's dimensions needs to be above both the minimum height and width for it to be processed.

Watch & compile changes: coffee --watch --output lib/ src/

It would be interesting to add support for sizes greater than @2x. If one specified @3x for example, this would generate both a @2x and normal version.