getColor method

Color getColor([
  1. Map<T, Color> colorStep = const {}
])

Get the color of a number based on a map of color steps. if the number is less than the minimum key, the color of the minimum key is returned. if the number is greater than the maximum key, the color of the maximum key is returned. if the number is between two keys, the color is interpolated between the two colors. if the number is equal to a key, the color of the key is returned. if the number is null, the color is transparent. if the color step is empty, the color is computed by converting the int value into Color using the default constuctor .

Implementation

Color getColor([Map<T, Color> colorStep = const {}]) {
  if (this == null) {
    return Colors.transparent;
  }

  if (colorStep.isEmpty) {
    return Color(this!.round());
  }

  T x = this!;
  if (colorStep.containsKey(x)) {
    return colorStep[x]!;
  }

  if (x <= colorStep.keys.min()!) {
    return colorStep[colorStep.keys.min()]!;
  }

  if (x >= colorStep.keys.max()!) {
    return colorStep[colorStep.keys.max()]!;
  }

  num lowerKey = -1 as num;
  num upperKey = -1 as num;

  for (var key in colorStep.keys) {
    if (key! < x && (lowerKey == -1 || key > lowerKey)) {
      lowerKey = key;
    }
    if (key > x && (upperKey == -1 || key < upperKey)) {
      upperKey = key;
    }
  }

  Color lowerColor = colorStep[lowerKey]!;
  Color upperColor = colorStep[upperKey]!;

  double proportion = (x - lowerKey) / (upperKey - lowerKey);
  return lowerColor.mixChannel(upperColor, proportion);
}