本文介绍了UIImage的CGImage返回NULL的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
我创建了一个将图像分割成多个图像的函数，但是当我拍摄UIImage的CGImage时，CGImage返回NULL
I created a function for splitting an image into multiple images, but when I take take the CGImage of the UIImage, the CGImage returns NULL
NSArray* splitImage(UIImage* image,NSUInteger pieces) {
NSLog(@"width: %f, %zu",image.size.width,CGImageGetWidth(image.CGImage));
NSLog(@"%@",image.CGImage);
returns NULL
NSMutableArray* tempArray = [[NSMutableArray alloc]initWithCapacity:pieces];
CGFloat piecesSize = image.size.height/pieces;
for (NSUInteger i = 0; i < pieces; i++) {
// take in account retina displays
CGRect subFrame = CGRectMake(0,i * piecesSize * image.scale ,image.size.width * image.scale,piecesSize * image.scale);
CGImageRef newImage = CGImageCreateWithImageInRect(image.CGImage,subFrame);
UIImage* finalImage =[UIImage imageWithCGImage:newImage];
CGImageRelease(newImage);
[tempArray addObject:finalImage];
}
NSArray* finalArray = [NSArray arrayWithArray:tempArray];
[tempArray release];
return finalArray;
}
推荐答案
如果UIImage是从另一个图像（如IOSurface或CIImage）创建的，则CGImage属性将返回nil。为了解决这个问题，我可以使用c函数从IOSurface创建一个CGImage，然后将其转换为UIImage。
The CGImage property will return nil if the UIImage was created from another image such as an IOSurface or CIImage. To get around this in this particular case I can create a CGImage from an IOSurface using the c function then convert that to a UIImage.
UICreateCGImageFromIOSurface(IOSurfaceRef surface);
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