ViewingConditions.make constructor

ViewingConditions.make((double, double, double) whitePoint, double adaptingLuminance, double backgroundLstar, double surround, bool discountingIlluminant,)

Create ViewingConditions from a simple, physically relevant, set of parameters.

Implementation

factory make(
  (double x, double y, double z) whitePoint,
  double adaptingLuminance,
  double backgroundLstar,
  double surround,
  bool discountingIlluminant,
) {
  // A background of pure black is non-physical and leads to infinities that represent the idea
  // that any color viewed in pure black can't be seen.
  backgroundLstar = math.max(0.1, backgroundLstar);
  // Transform white point XYZ to 'cone'/'rgb' responses
  const matrix = Cam16.xyzToCam16rgb;
  final xyz = whitePoint;
  final rW =
      xyz.$1 * matrix[0][0] + xyz.$2 * matrix[0][1] + xyz.$3 * matrix[0][2];
  final gW =
      xyz.$1 * matrix[1][0] + xyz.$2 * matrix[1][1] + xyz.$3 * matrix[1][2];
  final bW =
      xyz.$1 * matrix[2][0] + xyz.$2 * matrix[2][1] + xyz.$3 * matrix[2][2];
  final f = 0.8 + (surround / 10.0);
  final c = (f >= 0.9)
      ? MathUtils.lerp(0.59, 0.69, (f - 0.9) * 10.0)
      : MathUtils.lerp(0.525, 0.59, (f - 0.8) * 10.0);
  var d = discountingIlluminant
      ? 1.0
      : f *
            (1.0 -
                ((1.0 / 3.6) * math.exp((-adaptingLuminance - 42.0) / 92.0)));
  d = MathUtils.clamp(d, 0.0, 1.0);
  final nc = f;
  final rgbD = (
    d * (100.0 / rW) + 1.0 - d,
    d * (100.0 / gW) + 1.0 - d,
    d * (100.0 / bW) + 1.0 - d,
  );
  final k = 1.0 / (5.0 * adaptingLuminance + 1.0);
  final k4 = k * k * k * k;
  final k4F = 1.0 - k4;
  final fl =
      (k4 * adaptingLuminance) +
      (0.1 * k4F * k4F * math.pow(5.0 * adaptingLuminance, 1.0 / 3.0));
  final n = ColorUtils.yFromLstar(backgroundLstar) / whitePoint.$2;
  final z = 1.48 + math.sqrt(n);
  final nbb = 0.725 / math.pow(n, 0.2);
  final ncb = nbb;
  final rgbAFactors = <double>[
    math.pow(fl * rgbD.$1 * rW / 100.0, 0.42) as double,
    math.pow(fl * rgbD.$2 * gW / 100.0, 0.42) as double,
    math.pow(fl * rgbD.$3 * bW / 100.0, 0.42) as double,
  ];

  final rgbA = <double>[
    (400.0 * rgbAFactors[0]) / (rgbAFactors[0] + 27.13),
    (400.0 * rgbAFactors[1]) / (rgbAFactors[1] + 27.13),
    (400.0 * rgbAFactors[2]) / (rgbAFactors[2] + 27.13),
  ];

  final aw = ((2.0 * rgbA[0]) + rgbA[1] + (0.05 * rgbA[2])) * nbb;
  return ._(
    n,
    aw,
    nbb,
    ncb,
    c,
    nc,
    rgbD,
    fl,
    math.pow(fl, 0.25) as double,
    z,
  );
}