Quartz 2D: draw from a CGContext to another CGContext

Question

I have a CGBitmapContext ( bitmapContext ) and I would like to draw some rectangle part ( rect ) of it to the current CGContext ( context ).

Right now I do that way:

CGContextRef context = UIGraphicsGetCurrentContext();
CGImageRef cgImage = CGBitmapContextCreateImage(bitmapContext);
CGContextClipToRect(context, rect);
CGContextDrawImage(context, CGRectMake(0, 0, width, height), cgImage);
CGImageRelease(cgImage);

Is it optimal? What is the best way to do it?

Answer 1

替代方案似乎是创建一个子图像，我只能想象它不是最佳的。