photo.rb

  acts_as_fleximage do
    image_directory "/media/master_images"
    use_creation_date_based_directories true
    
    # image_storage_format    :jpg  # the plugin is handling this now
    require_image             true
    missing_image_message     'is required' 
    invalid_image_message     'was not a readable image'
    # default_image_path      'public/images/image_not_available.png'
    default_image             nil
    output_image_jpg_quality  85
  end

  def downloadable?(user)
    true # for now...
  end

photos_controller.rb

class PhotosController < ApplicationController
  FLEXI_METHODS.each {|flexi| caches_page flexi }

  FLEXI_METHODS.each do |flexi|
    define_method flexi do
      @photo = Photo.find(params[:id])
      render :template => "photos/flexi/#{flexi}"
    end
  end
  
  SEND_FILE_METHOD = :default

  def download
    head(:not_found) and return if (photo = Photo.find_by_id(params[:id])).nil?
    head(:forbidden) and return unless photo.downloadable?(current_user)

    path = "#{RAILS_ROOT}/media/photos/#{params[:id]}/#{params[:action_name]}.#{params[:format]}"
    head(:bad_request) and return unless File.exist?(path) && params[:format].to_s == File.extname(path).gsub(/^\.+/, '')

    send_file_options = { :type => File.mime_type?(path) }

    case SEND_FILE_METHOD
      when :apache then send_file_options[:x_sendfile] = true
      when :nginx then head(:x_accel_redirect => path.gsub(Rails.root, ''), :content_type => send_file_options[:type]) and return
    end

    send_file(path, send_file_options)
  end
end

routes.rb

  map.resources :photos, :has_many => :comments, :collection => { :destroy_album => :delete, :zip_import => :post, :builder_index => :get }, :member => FLEXI_METHODS.each_with_object({}){|string, hash| hash[string] = :get} # this returns  {:tiny_thumb_cover => :get, :builder_show => :get, etc...}

  map.connect 'images/:id/:action_name.:format', :controller => 'photos', :action => 'download', :conditions => { :method => :get }