Measure the luminance of a colour.

Input parameters:

1. C → Colour to measure.
2. M → Luminance metric.
   • 100 → Average
   • 101 → Desaturate
   • 102 → YCbCr (Photometric)
   • 103 → Hdtv (Photometric)
   • 104 → YCbCr (Gamma Adjusted)
   • 105 → Hdtv (Gamma Adjusted)
   • 106 → YCbCr (Perceived)
   • 107 → Hdtv (Perceived)

Output parameters:

1. L → Luminance of colour according to given metric.