Ruby: flag printer

flags.rb

#!/usr/bin/env ruby
require 'net/http'
require 'uri'

COLOR_SOURCE_VALUES = 256
COLOR_TARGET_VALUES = 5
COLOR_DIVIDE = COLOR_SOURCE_VALUES / COLOR_TARGET_VALUES
TERM_COLOR_BASE = 16

def rgb_to_xterm(r, g, b) # part of grosser.it/2011/09/16/ruby-converting-html-colors-24bit-to-xtermterminal-colors/
   r = (r / COLOR_DIVIDE) * 36
   g = (g / COLOR_DIVIDE) * 6
   b = (b / COLOR_DIVIDE) * 1

   TERM_COLOR_BASE + r + g + b
end

(ARGV.empty? ? ['USA'] : ARGV).each {|country|
   puts country
   page_uri = URI.parse("http:\//en.wikipedia.org/wiki/File:Flag_of_#{country}.svg")
   
   page_body = Net::HTTP.get_response(page_uri).body
   png_src = page_body.match(/fullImageLink.+ src="([^"]+)"/)[1]
   
   IO.popen("wget -q -O - http:#{png_src} | convert png:- -resize 80x -resize x55% rgb:-") {|io|
      while data = io.read(80*3)
         row = data.unpack('C*').each_slice(3).to_a
         row.map! {|rgb| "\e[48;5;#{rgb_to_xterm(*rgb)}m " }
         puts row.join + "\e[0m"
      end
   }
}