anchor.diff:  /// Convert a CIE-L*ab color to XYZ.
   List<int> labToXyz(num l, num a, num b) {
     num y = (l + 16.0) / 116.0;
  -  var x = y + (a / 500.0);
  -  var z = y - (b / 200.0);
  +  num x = y + (a / 500.0);
  +  num z = y - (b / 200.0);
     if (pow(x, 3) > 0.008856) {
       x = pow(x, 3);
     } else {
  
positive.code:     return [gray, gray, gray];
    }
  
    var h = (hue - hue.floor()) * 6.0;
    var f = h - h.floor();
    var p = brightness * (1.0 - saturation);
    var q = brightness * (1.0 - saturation * f);
    var t = brightness * (1.0 - (saturation * (1.0 - f)));
  
    switch (h.toInt()) {
      case 0:
  
negative.code:   g = g * 100.0;
    b = b * 100.0;
  
    num x = r * 0.4124 + g * 0.3576 + b * 0.1805;
    num y = r * 0.2126 + g * 0.7152 + b * 0.0722;
    num z = r * 0.0193 + g * 0.1192 + b * 0.9505;
  
    x = x / 95.047;
    y = y / 100.0;
  