iOS截取长图，自定义截取size

之前做过在查看商品详情时，需要截取很长的图片进行分享，已经超出一屏幕的显示范围：

- (UIImage *)captureScrollView:(UIScrollView *)scrollView {
    UIImage *image = nil;
    UIGraphicsBeginImageContextWithOptions(scrollView.contentSize, NO, 0.0);
    {
        CGPoint savedContentOffset = scrollView.contentOffset;
        CGRect savedFrame = scrollView.frame;
        scrollView.frame = CGRectMake(0 , 0, scrollView.contentSize.width, scrollView.contentSize.height);
        
        [scrollView.layer renderInContext:UIGraphicsGetCurrentContext()];
        image = UIGraphicsGetImageFromCurrentImageContext();
        
        scrollView.contentOffset = savedContentOffset;
        scrollView.frame = savedFrame;
    }
    UIGraphicsEndImageContext();
    
    if (image != nil) {
        return image;
    }
    return nil;
}