Broken or missing image interceptor

rack_image_interceptor.rb

# lib/rack_image_interceptor.rb

module Rack
  class ImageInterceptor
    def initialize(app)
      @app = app
    end

    def respond_with_placeholder_image(path)
      file = ::File.open(path)
      [200, {'Content-Type' => file.content_type}, [file.read]]
    end

    def call(env)
      case env['PATH_INFO']
      when /^\/system\/images\/[0-9]+\/(.+)$/
        placeholder_path = './public/images/placeholders'
        image_size = $1
        path_with_size = "#{placeholder_path}/property_placeholder_#{image_size}.gif"
        if ::File.exists?(path_with_size)
          respond_with_placeholder_image path_with_size
        elsif ::File.exists?("#{placeholder_path}/property_placeholder.gif")
          respond_with_placeholder_image("#{placeholder_path}/property_placeholder.gif")
        end
      when /^\/system\/avatars\/[0-9]+\/(.+)$/
        respond_with_placeholder_image('./public/images/user_thumb.png')
      else
        response = @app.call(env)
      end
    end

  end
end

# Then add this to your Rails environment file (e.g. development.rb)
# require 'lib/rack_image_interceptor.rb'       
# config.middleware.use ::Rack::ImageInterceptor