draw2dimg/ftgc.go
func (gc *GraphicContext) ClearRect(x1, y1, x2, y2 int) {
	imageColor := image.NewUniform(gc.Current.FillColor)
	draw.Draw(gc.img, image.Rect(x1, y1, x2, y2), imageColor, image.ZP, draw.Over)
}
func (gc *GraphicContext) ClearRect(x1, y1, x2, y2 int) {
	imageColor := image.NewUniform(gc.Current.FillColor)
	draw.Draw(gc.img, image.Rect(x1, y1, x2, y2), imageColor, image.ZP, draw.Over)
}
// ClearRect fills the current canvas with a default transparent color at the specified rectangle