ViewingConditions class Null safety

In traditional color spaces, a color can be identified solely by the observer's measurement of the color. Color appearance models such as CAM16 also use information about the environment where the color was observed, known as the viewing conditions.

For example, white under the traditional assumption of a midday sun white point is accurately measured as a slightly chromatic blue by CAM16. (roughly, hue 203, chroma 3, lightness 100)

This class caches intermediate values of the CAM16 conversion process that depend only on viewing conditions, enabling speed ups.