Dragonfly is a Rack framework for on-the-fly processing and encoding. It includes an extension for Ruby on Rails to enable easy image handling.

To use simply for image thumbnails etc. in Rails...

environment.rb (Rails 2.3 only):

config.gem 'rmagick',    :lib => 'RMagick'
config.gem 'rack-cache', :lib => 'rack/cache'
config.gem 'dragonfly'

Gemfile (Rails 3 only):

gem 'rmagick',    :require => 'RMagick'
gem 'rack-cache', :require => 'rack/cache'
gem 'dragonfly'

The above assumes that you have http://gemcutter.org as one of your gem sources. If not you should add it, e.g. gem source --add http://gemcutter.org from the command line, or add source http://gemcutter.org to your Gemfile.

Initializer (e.g. config/initializers/dragonfly.rb):

require 'dragonfly/rails/images'

Migration:

add_column :albums, :cover_image_uid, :string

Model:

class Album < ActiveRecord::Base
  image_accessor :cover_image            # Defines reader/writer for cover_image
  # ...
end

View (for uploading via a file field):

<% form_for @album, :html => {:multipart => true} do |f| %>
  ...
  <%= f.file_field :cover_image %>
  ...
<% end %>

View (to display):

<%= image_tag @album.cover_image.url(:gif) %>
<%= image_tag @album.cover_image.url('400x200') %>
<%= image_tag @album.cover_image.url('100x100!', :png) %>
<%= image_tag @album.cover_image.url('100x100#') %>
<%= image_tag @album.cover_image.url('50x50+30+30sw', :tiff) %>
<%= image_tag @album.cover_image.url(:rotate, 15) %>
...etc.

Dragonfly is primarily a Rack app, the Rails part of it being nothing more than a separate layer on top of the main code, which means you can use it as a standalone app, or with Sinatra, Merb, etc.

It is intended to be highly customizable, and is not limited to images, but any data type that could suit on-the-fly processing/encoding.

For more info, consult the DOCUMENTATION

Please use the github issue tracker if you have any issues.

Google group dragonfly-users

• Mark Evans (author)

Copyright (c) 2009-2010 Mark Evans. See LICENSE for details.