Simple paperclip processor that allows you to chain image styles.

Chainable.rb

#
# Chainable.rb
#
# Allows you to chain Paperclip styles.
# Created by Ed McManus for Yardsale Inc. on 5/12/2012
# 
#
# *********************************************************************
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
# 
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.
#
#
# Example - Optimized processing pipeline
# *********************************************************************
#
#  Copy to #{Rails.root}/lib/paperclip_processors/
#  Use OrderedHash prior to MRI 1.9.
#
#  has_attached_file :image,
#    :styles => {
#      :large => {
#        :geometry => "1000x1000^",
#        :format => :jpg,
#      },
#      :medium => {
#        :geometry => "640x640^",
#        :format => :jpg,
#        :chain_to => :large,
#        :processors => [:chainable, :thumbnail],
#      }
#      :small => {
#        :geometry => "160x160^",
#        :format => :jpg,
#        :chain_to => :medium,
#        :processors => [:chainable, :thumbnail],
#      }
#   }
#

# Chainable is a dummy processor that replaces the chain's accumulator value
# with the output of another style.
module Paperclip
  class Chainable < Processor
    def initialize file, options = {}, attachment = nil
      super attachment.queued_for_write.fetch(options[:chain_to], file), options, attachment
    end
    def make
      @file
    end
  end
end

Hi Ed,

It works great thanks, however it exposes an issue with Paperclip itself. The thumbnail processor builds a Tempfile using the passed filename as the base name (see thumbnail.make) and given the fact that styles are chained, names grow bigger and bigger. It ultimately leads to NameTooLong exception.

We fixed it in our project by extending the thumbnail processor and overriding the initialize method. We call super and set @basename to an empty string (it is only being used in the log and in the construction of the Tempfile).

Cheers,