image_degration_proxy.rb

#!/usr/bin/env ruby

require 'ubygems'
require 'webrick'
require 'webrick/httpproxy'
require 'RMagick'

q = {}
handler = Proc.new() do |req,res|
  if res.content_type =~ /jpeg/
    q[req.request_uri] ||= 100
    image = Magick::Image.from_blob(res.body)[0]
    res.body = image.to_blob do
      self.quality = q[req.request_uri] -= (q[req.request_uri] > 20 ? 10 : 0)
    end
    res['cache-control'] = 'no-cache'
  end
end

s = WEBrick::HTTPProxyServer.new(
  :BindAddress => '0.0.0.0',
  :Port => 8080,
  :ProxyContentHandler => handler
  )

Signal.trap('INT') do
  s.shutdown
end

s.start