Compute the channel values of a colour using the CMYK colour model.

Input parameters:

1. Cl → Colour to analyse.

Output parameters:

1. C → Value of the cyan channel in the $[0,1]$ range.
2. M → Value of the magenta channel in the $[0,1]$ range.
3. Y → Value of the yellow channel in the $[0,1]$ range.
4. K → Value of the key channel in the $[0,1]$ range.