Sets the color used for stroking shapes. r, g, b are 0-255, a is 0-1.
void setStrokeColorRgb(int r, int g, int b, [num a = 1]) {
  this.strokeStyle = 'rgba($r, $g, $b, $a)';
}
    © 2012 the Dart project authors
Licensed under the Creative Commons Attribution-ShareAlike License v4.0.
    https://api.dart.dev/stable/2.5.0/dart-html/CanvasRenderingContext2D/setStrokeColorRgb.html