# File lib/cairo/color.rb, line 116
      def to_cmyk
        cmy = [1.0 - @red, 1.0 - @green, 1.0 - @blue]
        key_plate = cmy.min
        if key_plate < 1.0
          one_k = 1.0 - key_plate
          cmyk = cmy.collect {|value| (value - key_plate) / one_k} + [key_plate]
        else
          cmyk = [0, 0, 0, key_plate]
        end
        cmyka = cmyk + [@alpha]
        CMYK.new(*cmyka)
      end