lstarToApcaY function

double lstarToApcaY(
  1. double lstar
)

Converts a CIE L* value to an APCA perceptual luminance (apcaY).

The path is L* → CIE Y → sRGB gamma (float) → APCA simpleExp. Uses delinearized for the transfer step, staying in float precision (no 8-bit quantization).

Implementation

double lstarToApcaY(double lstar) {
  final srgb = delinearized(yFromLstar(lstar) / 100.0);
  return (sRco + sGco + sBco) * math.pow(srgb.clamp(0.0, 1.0), mainTrc);
}