# File lib/prawn/svg/element.rb, line 166
  def color_to_hex(color_string)
    color_string.scan(/([^(\s]+(\([^)]*\))?)/).detect do |color, *_|
      if m = color.match(/\A#([0-9a-f])([0-9a-f])([0-9a-f])\z/i)
        break "#{m[1] * 2}#{m[2] * 2}#{m[3] * 2}"
      elsif color.match(/\A#[0-9a-f]{6}\z/i)
        break color[1..6]
      elsif hex = HTML_COLORS[color.downcase]
        break hex
      elsif m = color.match(RGB_REGEXP)
        break (1..3).collect do |n|
          value = m[n].to_f
          value *= 2.55 if m[n][-1..-1] == '%'
          "%02x" % clamp(value.round, 0, 255)
        end.join        
      end    
    end
  end