cat_avatar.rb

require 'rubygems'
require 'rmagick'
require 'digest'

def build_cat(seed=nil)
  srand(Digest::MD5.hexdigest(seed.to_s)[0...6].to_i(16)) if !seed.nil?

  # throw the dice for body parts
  parts = [
    ['body', rand(15)+1],
    ['fur', rand(10)+1],
    ['eyes', rand(15)+1],
    ['mouth', rand(10)+1],
    ['accessorie', rand(20)+1]
  ]

  # create background
  cat = Magick::Image.new(70, 70) { self.background_color = 'white' }
  cat.format = 'PNG'

  pwd = File.expand_path(File.dirname(__FILE__))

  # add parts
  parts.each do |data|
    part, num = data
    file = "#{pwd}/avatars/#{part}_#{num}.png"

    im = Magick::Image.read(file)[0]
    cat.composite!(im, 0, 0, Magick::SrcOverCompositeOp)
  end

  # restore random seed
  srand() if !seed.nil?

  return cat
end


def write_cat(seed)
  cat = build_cat(seed)

  File.open("cat#{seed}.png", 'w') do |f|
    f.write cat.to_blob
  end
end

write_cat(ARGV[0])