colorsNearestHSL function

List<String> colorsNearestHSL(String color, [ int n = 3 ])

The n css colors that are nearest in hsl space to color.

Example:

final color = "rgb(10, 20, 30)";
for (final c in colorsNearestHSL(color, 3)) {
  print(c);
}

Output:

midnightblue
darkslategray
darkslateblue

Implementation

List<String> colorsNearestHSL(String color, [int n = 3]) {
  final ps = ColorProperties(color), hue = ps.hueInDegrees;
  if (hue == null) throw Exception("Hue not defined for $color.");
  final saturation = ps.saturation,
      lightness = ps.lightness,
      distanceTuple = (String color) {
        final ps = ColorProperties(color), h = ps.hueInDegrees;
        if (h == null) return null;

        final greater = h > hue ? h : hue,
            lesser = h < hue ? h : hue,
            d = greater - lesser;

        final dp = (d > 180 ? 360 - d : d) / 180,
            s = ps.saturation - saturation,
            l = ps.lightness - lightness;
        return (color, dp * dp + s * s + l * l);
      },
      hueDifferences = [
        ...Color.colorData.keys.map(distanceTuple).where((d) => d != null)
      ]..sort((a, b) => _byDistance(a!, b!));

  return [...hueDifferences.sublist(0, n).map((t) => _getColor(t!))];
}