Dynamic, image-resizing rack application

config.ru

require 'rack'
require 'rack/cache'
require './squint'

use Rack::Chunked

use Rack::Cache,
  :verbose => true,
  :allow_reload => false,
  :metastore => 'file:cache/meta',
  :entitystore => 'file:cache/ent',
  :private_headers => ['Authorization'],
  :default_ttl => 5000

run Rack::Squint.new('.', 1000, 1000)

squint.rb

require 'stringio'
require 'rubygems'
require 'rack/utils'
require 'axon'

module Rack
  class Squint < File
    class ImageBody
      def initialize(path, width, height)
        @path = path
        @width = width
        @height = height
      end
  
      def each
        strio = StringIO.new

        Axon.jpeg_file(@path) do |im|
          im.fit(@width || im.width, @height || im.height)
          im.jpeg(strio)
          yield strio.string
        end
      end
    end

    def initialize(root, max_width, max_height)
      @max_width = max_width
      @max_height = max_height
      super(root)
    end
    
    def serving(env)
      header = { "Last-Modified" => F.mtime(@path).httpdate }
      header["Content-Type"] = 'image/jpeg'
      
      if env["REQUEST_METHOD"] == "HEAD"
        [200, header, []]
      else
        qs = Utils.parse_query(env["QUERY_STRING"])
        width = sane_dimension(qs['width'].to_i, @max_width)
        height = sane_dimension(qs['height'].to_i, @max_height)
        [200, header, ImageBody.new(@path, width, height)]
      end
    end

    private

    def sane_dimension(dim, max)
      if max && dim > max then max
      elsif dim < 1 then nil
      else dim
      end
    end
  end
end