结合UIImageViews产生0字节的空图像

Question

我试图合并两个UIImageView一起到combinedView。我遇到的问题是，在将self.firstImageView和self.secondImageView作为子视图添加到我的combinedView之后，当我检查combinedView.image的字节大小时，我得到的输出为0.我需要combinedView.image最终传递到JEPGRepresentation中的后端，所以我不确定我怎么可能将这些观点结合在一起，或者我目前做错了什么。

感谢您的帮助！

UIImageView *combinedView = [[UIImageView alloc] init]; 
[combinedView addSubview:self.firstImageView]; 
[combinedView sendSubviewToBack:self.firstImageView]; 
[combinedView addSubview:self.secondImageView]; 
[combinedView bringSubviewToFront:self.secondImageView]; 

NSData *firstPicData = UIImageJPEGRepresentation(self.firstImageView.image, 1.0); 
NSLog(@"Size of first:%d",[firstPicData length]); //outputs a non-zero number 

NSData *secondPicData = UIImageJPEGRepresentation(self.secondImageView.image, 1.0); 
NSLog(@"Size of second:%d",[secondPicData length]); //also outputs a non-zero number 

NSData *combinedPicData = UIImageJPEGRepresentation(combinedView.image, 1.0); 
NSLog(@"Size of combined:%d",[combinedPicData length]); //! outputs 0 bytes 

Answer 1

你加入self.firstImageView和self.secondImageView作为组合视图和多过你没有分配到任何combinedView图像的子画面。所以[combinedPicData length]总是只有0。

请参考以下链接合并两幅图像。

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