Rack application that returns image information as JSON

config.ru

require 'rack'
require './jimmy'

run Rack::Jimmy.new('.')

jimmy.rb

require 'rubygems'
require 'json'
require 'rack/utils'
require 'time'
require 'axon'

module Rack
  class Jimmy < File
    class ImageJSON
      def initialize(path)
        @path = path
      end

      def each
        Axon.jpeg_file(@path) do |im|
          json = { :width => im.width, :height => im.height }.to_json
          yield json
        end
      end
    end
    
    def serving(env)
      header = { "Last-Modified" => F.mtime(@path).httpdate }
      header["Content-Type"] = "application/json"
      
      if env["REQUEST_METHOD"] == "HEAD"
        [200, header, []]
      else
        [200, header, ImageJSON.new(@path)]
      end
    end
  end
end