保存图片

- (void)saveImage
{
    int index = _scrollView.contentOffset.x / _scrollView.bounds.size.width;
    UIImageView *currentImageView = _scrollView.subviews[index];
    
    UIImageWriteToSavedPhotosAlbum(currentImageView.image, self, @selector(image:didFinishSavingWithError:contextInfo:), NULL);
    
    UIActivityIndicatorView *indicator = [[UIActivityIndicatorView alloc] init];
    indicator.activityIndicatorViewStyle = UIActivityIndicatorViewStyleWhiteLarge;
    indicator.center = self.center;
    _indicatorView = indicator;
    [[UIApplication sharedApplication].keyWindow addSubview:indicator];
    [indicator startAnimating];
}

- (void)image:(UIImage *)image didFinishSavingWithError:(NSError *)error contextInfo:(void *)contextInfo;
{
    [_indicatorView removeFromSuperview];
    
    UILabel *label = [[UILabel alloc] init];
    label.textColor = [UIColor whiteColor];
    label.backgroundColor = [UIColor colorWithRed:0.1f green:0.1f blue:0.1f alpha:0.90f];
    label.layer.cornerRadius = 5;
    label.clipsToBounds = YES;
    label.bounds = CGRectMake(0, 0, 150, 30);
    label.center = self.center;
    label.textAlignment = NSTextAlignmentCenter;
    label.font = [UIFont boldSystemFontOfSize:17];
    [[UIApplication sharedApplication].keyWindow addSubview:label];
    [[UIApplication sharedApplication].keyWindow bringSubviewToFront:label];
    if (error) {
        label.text = SDPhotoBrowserSaveImageFailText;
    }   else {
        label.text = SDPhotoBrowserSaveImageSuccessText;
    }
    [label performSelector:@selector(removeFromSuperview) withObject:nil afterDelay:1.0];
}