# File lib/captcha.rb, line 285
    def to_html( template_file=nil )
      template = File.open( ( template_file || @template_file ), "r" ) { |file| file.read }

      template.gsub( /%%IMAGE%%/, file_name ).
               gsub( /%%IMAGEURI%%/, @image_uri ).
               gsub( /%%DIGEST%%/, @digest ).
               gsub( /%%IMAGEWIDTH%%/, image.width.to_s ).
               gsub( /%%IMAGEHEIGHT%%/, image.height.to_s )
    end