gistfile1.txt

require 'webrick/httpproxy'
require 'RMagick'

handler = Proc.new do |req,res|
  if [".gif", ".png", ".jpg", ".jpeg", ".ico"].include? req.path[-4..-1]
    begin
      image = Magick::Image.from_blob(res.body).first
      image.flip!
      res.body = image.to_blob
    rescue Magick::ImageMagickError => e
      puts "#{req.path} error:#{e}"
    end
  end
end

server = WEBrick::HTTPProxyServer.new(:Port => 9090, :AccessLog => [],
                                      :ProxyContentHandler => handler)

trap("INT") { server.shutdown }
server.start