在arc模式下 CGImage 释放问题

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一直以为 arc模式下什么东西都可以自动去释放不需要自己去管理
后来才发现根本不是那么回事

//裁减图片

-(UIImage *)getImageFromImage:(UIImage *)i :(int)imagecount{

//大图bigImage

//定义myImageRect，截图的区域

if (imagecount >= 3) {

CGRect myImageRect;

if (i.size.width<= i.size.height) {

myImageRect = CGRectMake(0.0,150.0, i.size.width, i.size.width);

}

else

myImageRect = CGRectMake(0.0,150.0, i.size.height, i.size.height);

UIImage* bigImage= i;

CGImageRef imageRef = bigImage.CGImage;

CGImageRef subImageRef = CGImageCreateWithImageInRect(imageRef, myImageRect);

CGSize size;

size.width = 80;

size.height = 80;

UIGraphicsBeginImageContext(size);

CGContextRef context =UIGraphicsGetCurrentContext();

CGContextDrawImage(context, myImageRect, subImageRef);

UIImage* smallImage = [UIImageimageWithCGImage:subImageRef];

CGImageRelease(subImageRef);

UIGraphicsEndImageContext();

return smallImage;

}

if (imagecount < 3) {

CGRect myImageRect;

if (i.size.width<= i.size.height) {

myImageRect = CGRectMake(0.0,150.0, i.size.width, i.size.width*2/3);

}

else

myImageRect = CGRectMake(0.0,150.0, i.size.height, i.size.height*2/3);

UIImage* bigImage= i;

CGImageRef imageRef = bigImage.CGImage;

CGImageRef subImageRef = CGImageCreateWithImageInRect(imageRef, myImageRect);

CGSize size;

size.width = 120;

size.height = 80;

UIGraphicsBeginImageContext(size);

CGContextRef context =UIGraphicsGetCurrentContext();

CGContextDrawImage(context, myImageRect, subImageRef);

UIImage* smallImage = [UIImageimageWithCGImage:subImageRef]; //注意蓝色的部分

CGImageRelease(subImageRef);

return smallImage;

}

return nil;

}

像这样裁剪图片就会有内存泄漏

后来上 stackoverflow 查找发现这样一段话

ARC does not manage C-types, of which CGImage may be considered. You must release the ref manually when you are finished with CGImageRelease(image);

UIImage* smallImage = [UIImage imageWithCGImage:subImageRef];

CGImageRelease(subImageRef);

UIGraphicsEndImageContext();

也就是在arc模式下不是什么东西都可以释放例如 C-types的对象都需要手动来进行释放

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