markevans/dragonfly — pull request #355 by teknofire (2014-08-07 19:03:51+00:00)
Title: adding support for specifying a delegate option to imagemagick

This is to allow for custom processing of files through imagemagick using it's built in delegate handling. We are using this to generate thumbnails from movies

Simple example of use case:
```ruby
class Movie < ActiveRecord::Base
extend Dragonfly::Model
dragonfly_accessor :preview
dragonfly_accessor :file do
copy_to(:preview) do |mov|
mov.convert("", 'format' => 'jpg', 'frame' => 1, 'delegate' => 'ffmpeg')
end
end
end
```