cvdDeltaE function
ΔEOK between argbA and argbB as seen under type (null = normal
vision).
Implementation
double cvdDeltaE(int argbA, int argbB, [Cvd? type]) {
final a = argbToLin(argbA);
final b = argbToLin(argbB);
if (type == null) return deltaEOK(linToOklab(a), linToOklab(b));
return deltaEOK(
linToOklab(simulateCvd(a, type)),
linToOklab(simulateCvd(b, type)),
);
}