ios - UIGraphics 内存泄漏

Question

- (UIImage *)deleteBackgroundOfImage:(UIImageView *)image
{
    CGRect rect = CGRectZero;
    rect.size = image.image.size;

    UIGraphicsBeginImageContextWithOptions(rect.size, YES, 0.0);

    UIImage *mask = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    UIGraphicsBeginImageContextWithOptions(rect.size, NO, 0.0);

    {
        CGContextClipToMask(UIGraphicsGetCurrentContext(), rect, mask.CGImage);
        [image.image drawAtPoint:CGPointZero];
    }

    UIImage *maskedImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return maskedImage;
}

当我两次调用上述函数时，我得到“收到内存警告”，任何人都可以告诉我泄漏的位置。提前谢谢。