dx method
Implementation
Color dx(double percentage) {
assert(percentage >= 0 && percentage <= 100);
final x = (percentage / 100 * 255).round();
final base = this ?? Colors.transparent;
int r = base.red - x;
int g = base.green - x;
int b = base.blue - x;
if (r < 0) r = 0;
if (g < 0) g = 0;
if (b < 0) b = 0;
return Color.fromARGB(base.alpha, r, g, b);
}