Dragonfly

Dragonfly is a Rack framework for on-the-fly image handling.

Ideal for using with Ruby on Rails (2.3 and 3), Sinatra and all that gubbins.

However, Dragonfly is NOT JUST FOR RAILS, and NOT JUST FOR IMAGES!!

IMPORTANT: if you're running a version between 0.7.0 and 0.9.12, please update to at least 0.9.14 for a security update details here

For the lazy Rails user...

Gemfile:

gem 'rack-cache', :require => 'rack/cache'
gem 'dragonfly', '~>0.9.15'

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

require 'dragonfly/rails/images'

Migration:

add_column :albums, :cover_image_uid,  :string
add_column :albums, :cover_image_name, :string  # Optional - only if you want urls
                                                # to end with the original filename

Model:

class Album < ActiveRecord::Base
  image_accessor :cover_image            # 'image_accessor' is provided by Dragonfly
                                         # this defines a 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 %>

NB: REMEMBER THE MULTIPART BIT!!!

You can avoid having to re-upload when validations fail with

<%= f.hidden_field :retained_cover_image %>

remove the attachment with

<%= f.check_box :remove_cover_image %>

assign from some other url with

<%= f.text_field :cover_image_url %>

and display a thumbnail (on the upload form) with

<%= image_tag @album.cover_image.thumb('100x100').url if @album.cover_image_uid %>

View (to display):

<%= image_tag @album.cover_image.url %>
<%= image_tag @album.cover_image.thumb('400x200#').url %>
<%= image_tag @album.cover_image.jpg.url %>
<%= image_tag @album.cover_image.process(:greyscale).encode(:tiff).url %>
...etc.

The above relies on imagemagick being installed. Dragonfly doesn't depend on it per se, but the default configuration 'dragonfly/rails/images' uses it. For alternative configurations, see below.

If using Capistrano with the above, you probably will want to keep the cache between deploys, so in deploy.rb:

namespace :dragonfly do
  desc "Symlink the Rack::Cache files"
  task :symlink, :roles => [:app] do
    run "mkdir -p #{shared_path}/tmp/dragonfly && ln -nfs #{shared_path}/tmp/dragonfly #{release_path}/tmp/dragonfly"
  end
end
after 'deploy:update_code', 'dragonfly:symlink'

Sinatra, CouchDB, Mongo, Rack, S3, custom storage, processing, and more...

Dragonfly is not just for Rails - it's primarily a Rack app, so you can use it as a standalone app, or with Sinatra, Merb, etc.

It's highly customizable, and works with any data type (not just images).

For more info, consult the DOCUMENTATION

Add-ons

For third-party add-ons, see the Add-ons wiki

Issues

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

Suggestions/Questions

Google group dragonfly-users

Credits

Mark Evans (author)