Many image processing algorithms are defined for grayscale (or else monochromatic) images.



Task

Extend the data storage type defined on this page to support grayscale images.

Define two operations, one to convert a color image to a grayscale image and one for the backward conversion.

To get luminance of a color use the formula recommended by CIE:

 L  =  0.2126 × R   +   0.7152 × G   +   0.0722 × B 

When using floating-point arithmetic make sure that rounding errors would not cause run-time problems or else distorted results when calculated luminance is stored as an unsigned integer.




class RGBColour
  def to_grayscale
    luminosity = (0.2126*@red + 0.7152*@green + 0.0722*@blue).to_i
    self.class.new(luminosity, luminosity, luminosity)
  end
end
 
class Pixmap
  def to_grayscale
    gray = self.class.new(@width, @height)
    @width.times do |x|
      @height.times do |y|
        gray[x,y] = self[x,y].to_grayscale
      end
    end
    gray
  end
end