darken function
Implementation
Color darken(Color color, ShadowDegree degree) {
double amount = degree == ShadowDegree.dark ? 0.3 : 0.12;
final hsl = HSLColor.fromColor(color);
final hslDark = hsl.withLightness((hsl.lightness - amount).clamp(0.0, 1.0));
return hslDark.toColor();
}