以编程方式截取屏幕截图非常慢

Question

我有下面的代码，每次加载大约需要7-10秒，我想优化它，让它在一秒钟或更短的时间内将屏幕截图和加载共享。

UIImage *imageToShare = [self screenshot];
NSArray *activityItems = @[stringToShare, imageToShare];
UIActivityViewController *activityVC = [[UIActivityViewController alloc] initWithActivityItems:activityItems applicationActivities:nil];
activityVC.excludedActivityTypes = @[UIActivityTypeAssignToContact, UIActivityTypePrint, UIActivityTypePostToWeibo];
[self presentViewController:activityVC animated:TRUE completion:nil];

- (UIImage *) screenshot {
    UIGraphicsBeginImageContextWithOptions(self.view.bounds.size, NO, [UIScreen mainScreen].scale);

    [self.view drawViewHierarchyInRect:self.view.bounds afterScreenUpdates:YES];

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

我不太确定如何才能让它运行得更快？有什么想法吗？