Given an XYZ color whose components are in the nominal range [0.0, 1.0]:

**Implementation Notes:**

- Watch out for black, where
*X*=*Y*=*Z*= 0. In that case, you may want to set*x*and*y*to the chromaticity coordinates of your reference white. - The output Y value is in the nominal range [0.0, 1.0].