Convert 'hatena tex' to google chart

google_tex.rb

require 'cgi'
google_url = "http://chart.apis.google.com/chart?cht=tx&chl="
$<.each{|l|
  l.chomp!
  l.scan(/(\[tex:(.*?)\]){1,}/).each do |e|
    math = e[1]
    url_math = CGI.escape(math)
    l.sub!(/#{Regexp.quote(e[0])}/,"<img src=\"#{google_url}#{url_math}\">")
  end
  puts l
}