iOS UIScrollView 截取高清图片

- (UIImage *)captureScrollView:(UIScrollView *)scrollView{
    UIImage* image = nil;
    UIGraphicsBeginImageContext(scrollView.contentSize);
    {
        CGPoint savedContentOffset = scrollView.contentOffset;
        CGRect savedFrame = scrollView.frame;
        scrollView.contentOffset = CGPointZero;
        scrollView.frame = CGRectMake(0, 20, scrollView.contentSize.width, 20 * 2 + 70 + 930 / 2.0 );
        UIGraphicsBeginImageContextWithOptions(scrollView.frame.size, NO, [UIScreen mainScreen].scale);
        [scrollView.layer renderInContext: UIGraphicsGetCurrentContext()];
        image = UIGraphicsGetImageFromCurrentImageContext();
        
        scrollView.contentOffset = savedContentOffset;
        scrollView.frame = savedFrame;
    }
    UIGraphicsEndImageContext();
    
    if (image != nil) {
        return image;
    }
    return nil;
}