剪切图像时iOS收到内存警告

Question

I tried to cut the image after taking photos. This works fine on Non-Retina Device. But received memory warning on Retina Device. I think there are some memory leaks when cutting the image cuz when I commented out, no issues.

Code:

- (void) imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info
{
    UIImage *image = [info objectForKey:UIImagePickerControllerOriginalImage];
    CGSize imageSize = image.size;
    CGFloat width = imageSize.width;
    CGFloat height = imageSize.height;
    CGFloat newDimension = 2360;
    CGFloat widthOffset = 20 * [[UIScreen mainScreen] scale];
    CGFloat heightOffset = 135 * [[UIScreen mainScreen] scale];

    UIGraphicsBeginImageContextWithOptions(CGSizeMake(newDimension, newDimension), NO, 0.);
    [image drawAtPoint:CGPointMake(-widthOffset, -heightOffset)
             blendMode:kCGBlendModeCopy
                 alpha:1.];

    productImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    [self dismissViewControllerAnimated:NO completion:nil];

    ...
}

First time after taking photo, I got memory warning but not crashed. When I try to reopen camera the app crashed. Can somebody help me out? Thanks

Answer 1

@autoreleasepool {
    ...
    productImage = UIGraphicsGetImageFromCurrentImageContext();
    ...
}

autoreleasepool might help it. UIGraphicsGetImageFromCurrentImageContext returns autoreleased UIImage object and it remains for awhile until exiting autoreleasepool block or the end of the runloop on the main thread. Which part of your code should be enclosed by autoreleasepool, it depends on your code.