application.rb

require File.expand_path('../boot', __FILE__)

require 'rails/all'

# If you have a Gemfile, require the gems listed there, including any gems
# you've limited to :test, :development, or :production.
Bundler.require(:default, Rails.env) if defined?(Bundler)

module Slideshowbob
  class Application < Rails::Application
    # Settings in config/environments/* take precedence over those specified here.
    # Application configuration should go into files in config/initializers
    # -- all .rb files in that directory are automatically loaded.

    # Custom directories with classes and modules you want to be autoloadable.
    # config.autoload_paths += %W(#{config.root}/extras)

    # Only load the plugins named here, in the order given (default is alphabetical).
    # :all can be used as a placeholder for all plugins not explicitly named.
    # config.plugins = [ :exception_notification, :ssl_requirement, :all ]

    # Activate observers that should always be running.
    # config.active_record.observers = :cacher, :garbage_collector, :forum_observer

    # Set Time.zone default to the specified zone and make Active Record auto-convert to this zone.
    # Run "rake -D time" for a list of tasks for finding time zone names. Default is UTC.
    # config.time_zone = 'Central Time (US & Canada)'

    # The default locale is :en and all translations from config/locales/*.rb,yml are auto loaded.
    # config.i18n.load_path += Dir[Rails.root.join('my', 'locales', '*.{rb,yml}').to_s]
    # config.i18n.default_locale = :de

    # JavaScript files you want as :defaults (application.js is always included).
    # config.action_view.javascript_expansions[:defaults] = %w(jquery rails)

    # Configure the default encoding used in templates for Ruby 1.9.
    config.encoding = "utf-8"

    # Configure sensitive parameters which will be filtered from the log file.
    config.filter_parameters += [:password]
    
    # Needed for paperclip: http://github.com/thoughtbot/paperclip/issues/issue/247
    # The documentation states that custom processors that inherit from Paperclip::Processor will be loaded
    # automatically if placed in lib/paperclip_processors. But in Rails 3, this isn't the case.
    # This issue is caused by the Paperclip gem being loaded before the Rails object is properly configured.
    # Needs to be fixed properly in Paperclip itself.
    config.after_initialize do
      # copied from paperclip.rb: due to bundler, this doesn't seem to happen automagically anymore!?!
      Dir.glob(File.join(File.expand_path(Rails.root), "lib","paperclip_processors", "*.rb")).each do |processor|
        require processor # PVDB don't rescue LoadError... let it rip!
      end
    end
    
  end
end

photo.rb

class Photo < ActiveRecord::Base
  belongs_to :show
  
  validates :ken_burns_start_zoom, :presence => true, :numericality => true
  validates :ken_burns_end_zoom, :presence => true, :numericality => true
  validates :duration, :presence => true, :numericality => true
  
  # Paperclip
  has_attached_file :image,
      :storage => :s3,
      :processors => [:thumbnail,:watermark],
      :s3_credentials => "#{Rails.root}/config/amazon_s3.yml",
      :path => "photos/:id/image/:normalized_image_file_name_:style.:extension",
      :url => ":s3_alias_url",
      :s3_host_alias => "#{S3Config[:bucket]}.s3.amazonaws.com",
      :styles => {
        :square_25  => {
          :geometry => '25x25#',
          :watermark_path => "#{Rails.root}/public/images/watermarks/square_25.png",
          :watermark_position => "Center"
        },
        :square_1x  => {
          :geometry => '100x100#',
          :watermark_path => "#{Rails.root}/public/images/watermarks/square_1x.png",
          :watermark_position => "Center"
        },
        :scaled_1x  => {
          :geometry => '100x67',
          :watermark_path => "#{Rails.root}/public/images/watermarks/scaled_1x.png",
          :watermark_position => "Center"
        },
        :scaled_2x  => {
          :geometry => '220x147',
          :watermark_path => "#{Rails.root}/public/images/watermarks/scaled_2x.png",
          :watermark_position => "Center"
        },
        :scaled_3x  => {
          :geometry => '340x227',
          :watermark_path => "#{Rails.root}/public/images/watermarks/scaled_3x.png",
          :watermark_position => "Center"
        },
        :scaled_4x  => {
          :geometry => '460x307',
          :watermark_path => "#{Rails.root}/public/images/watermarks/scaled_4x.png",
          :watermark_position => "Center"
        },
        :scaled_6x  => {
          :geometry => '700x467',
          :watermark_path => "#{Rails.root}/public/images/watermarks/scaled_6x.png",
          :watermark_position => "Center"
        },
        :scaled_8x  => {
          :geometry => '940x627',
          :watermark_path => "#{Rails.root}/public/images/watermarks/scaled_8x.png",
          :watermark_position => "Center"
        }
      },
      :whiny => true

      
  # http://blog.wyeworks.com/2009/7/13/paperclip-file-rename
  Paperclip.interpolates :normalized_image_file_name do |attachment, style|
    attachment.instance.normalized_image_file_name
  end
  
  Photo::KenBurnsPositions = ['Center','North','NorthEast','East','SouthEast','South','SouthWest','West','NorthWest']

  # http://blog.wyeworks.com/2009/7/13/paperclip-file-rename
  def normalized_image_file_name
    # Regex strips the file extension
    self.image_file_name[/.*(?=\..+$)/].gsub( /[^a-zA-Z0-9_]/, '_') 
  end
  
  def image_file_extension
    self.image_file_name[/\.([^\.]+)$/]
  end
end

watermark.rb

# /lib/paperclip_processors/watermark.rb

# from http://github.com/ng/paperclip-watermarking-app with modifications

module Paperclip
  class Watermark < Processor

    def initialize file, options = {}, attachment = nil
       super
       @file             = file
       @format           = options[:format]
       @current_format   = File.extname(@file.path)
       @basename         = File.basename(@file.path, @current_format)
       
       @watermark_path   = options[:watermark_path]
       @watermark_position = options[:watermark_position].nil? ? "SouthEast" : options[:watermark_position]
     end

      # Performs the conversion of the +file+ into a watermark. Returns the Tempfile
      # that contains the new image.
      def make
        src = @file
        dst = Tempfile.new([@basename, @format ? ".#{@format}" : ''])
        dst.binmode

        if @watermark_path
          parameters = []
          parameters << "-gravity"
          parameters << @watermark_position
          parameters << ":watermark"
          parameters << ":source"
          parameters << ":dest"
          
          parameters = parameters.flatten.compact.join(" ").strip.squeeze(" ")

          begin
            success = Paperclip.run(
              'composite', 
              parameters, 
              :source => "#{File.expand_path(src.path)}[0]", 
              :dest => File.expand_path(dst.path),
              :watermark => File.expand_path(@watermark_path)
            )
          rescue PaperclipCommandLineError
            raise PaperclipError, "There was an error processing the watermark for #{@basename}" if @whiny
          end
        end

        dst
      end

  end
end