gistfile1.rb

#!/usr/bin/env ruby
require 'nokogiri'
require 'open-uri'
url = 'http://www.melon-peach.com'
ua = 'Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.5; en-US; rv:1.9.1.2) Gecko/20090729 Firefox/3.5.2'
html = Nokogiri.parse(open(url, 'User-Agent' => ua).read)
html.xpath('//img[contains(@src, "/small")]').each_with_index do |img, i|
  data = open(url + '/userimages/' + img['src'].sub(%r{/small}, '/big'), 'User-Agent' => ua).read
  data.gsub!(
    /\xFF\xDA\x00\x0C\x03\x01[\s\S]\x02[s\S]\x03[\s\S]/, 
    "\xFF\xDA\x00\x0C\x03\x01\x11\x02\x11\x03\x00"
  )
  File.open("#{'%02d' % i}.jpg", 'w') {|f| f.write data }
end