func (gc *GraphicContext) paint(rasterizer *raster.Rasterizer, color color.Color) {
gc.painter.SetColor(color)
rasterizer.Rasterize(gc.painter)
rasterizer.Clear()
gc.painter.Flush()
gc.Current.Path.Clear()
}
func rasterBbox(rasterizer *raster.Rasterizer) (r image.Rectangle) {
var bbox bboxPainter
rasterizer.Rasterize(&bbox)
return bbox.R
}