Compute the channel values of a colour using the Lab* colour model.

Input parameters:

1. Cl → Colour to analyse.

Output parameters:

1. L* → Value of the luminance channel in the $[0,100]$ range.
2. A* → Value of the (green, red) opposition channel. Nominally within $[-50,+50]$, though saturated colours exceed that.
3. B* → Value of the (blue, yellow) opposition channel. Nominally within $[-50,+50]$, though saturated colours exceed that.