code: func (dc *Context) SetRGBA255(r, g, b, a int) {
  	dc.color = color.NRGBA{uint8(r), uint8(g), uint8(b), uint8(a)}
  	dc.setFillAndStrokeColor(dc.color)
  }
docs: // SetRGBA255 sets the current color. r, g, b, a values should be between 0 and
  // 255, inclusive.