Programmatically Lighten or Darken a hex color in dart

Question

I am trying to convert this hash color code #159424 (GREEN-COLOR) to more darken and lighten programmatically. How to do this please help?

make green color darker

toDarkColor(String hashColor){
  // how to convert that hash string to make green color darker?
}

make green color lighter

toLightColor(String hashColor){
  // how to convert that hash string to make green color lighter? 
}

Answer 1

For people who want to darken or lighten Color instead of hex string

// ranges from 0.0 to 1.0

Color darken(Color color, [double amount = .1]) {
  assert(amount >= 0 && amount <= 1);

  final hsl = HSLColor.fromColor(color);
  final hslDark = hsl.withLightness((hsl.lightness - amount).clamp(0.0, 1.0));

  return hslDark.toColor();
}

Color lighten(Color color, [double amount = .1]) {
  assert(amount >= 0 && amount <= 1);

  final hsl = HSLColor.fromColor(color);
  final hslLight = hsl.withLightness((hsl.lightness + amount).clamp(0.0, 1.0));

  return hslLight.toColor();
}

// usage
final lightRed = lighten(Colors.red);
final darkBlue = darken(Colors.blue, .3);

Live Demo