rgbaToHex function
Implementation
int rgbaToHex(int red, int green, int blue, {double opacity = 1}) {
red = (red < 0) ? -red : red;
green = (green < 0) ? -green : green;
blue = (blue < 0) ? -blue : blue;
opacity = (opacity < 0) ? -opacity : opacity;
opacity = (opacity > 0) ? 255 : opacity * 255;
red = (red > 255) ? 255 : red;
green = (green > 255) ? 255 : green;
blue = (blue > 255) ? 255 : blue;
int alpha = opacity.toInt();
final String hex =
'0x${alpha.toRadixString(16)}${red.toRadixString(16)}${green.toRadixString(16)}${blue.toRadixString(16)}';
return int.parse(hex.replaceFirst('-', ''));
}