将CGImageRef(不是UIImage)绘制到图像上下文中

Question

以下是如何在上下文中绘制UIImage:

UIGraphicsBeginImageContextWithOptions(size, NO, 0.0f);
[someUIImage drawInRect:CGRectMake(...)];
[someOtherUIImage drawInRect:CGRectMake(...)];
[someOtherUIImage drawInRect:CGRectMake(...)];
UIImage *yourResult = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

没问题.但是,假设我有一个以某种方式构建的CGImageRef.

CGImageRef happyImageRef = CGImageCreateWithImageInRect(blah blah);

我想把它绘制到上下文中.

UIGraphicsBeginImageContextWithOptions(size, NO, 0.0f);
[ happyImageRef .. somehowDrawInRect:CGRectMake(...)];
UIImage *yourResult = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

你是怎样做的？

要清楚,显然你可以将它转换为UIImage

UIImage *wasteful = [UIImage imageWithCGImage:happyImageRef];

但这看起来非常低效.怎么做？

我确定我很困惑或遗漏了一些简单的东西,谢谢.

Answer 1

使用CGContextDrawImage

UIGraphicsBeginImageContextWithOptions(size, NO, 0.0f);
CGContextDrawImage(UIGraphicsGetCurrentContext(),CGRectMake(...), happyImageRef);
UIImage *yourResult = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();