OklabColor constructor
A color in the Oklab color space.
lightness, a, and b's normal range is 0.0 to 1.0,
but some colors may fall slightly outside of it.
alpha must be >= 0 and <= 255.
Implementation
const OklabColor(
double lightness,
double a,
double b, [
int alpha = 255,
]) : assert(alpha >= 0 && alpha <= 255),
super(lightness, a, b, alpha);