rgb2css function
returns an rgba css string like rgba(255, 255, 255, 1)
from the rgb color and alpha value
Implementation
String rgb2css(num alpha, List<num> color) {
var rgb = color.map((e) => _clamp(0, 255, e.round())).toList();
var r = rgb[0];
var g = rgb[1];
var b = rgb[2];
return 'rgba($r, $g, $b, ${_clampNorm(alpha)})';
}