如何给一个ScrollView添加一个水印, 或者添加一些文字或截图

• (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {

  CGSize scrollViewSize = CGSizeMake(self.scrollView.frame.size.width, self.scrollView.frame.size.height);

  // 1. 开启位图上下文
  UIGraphicsBeginImageContextWithOptions(scrollViewSize, 0, 1);

  // 2. 获取当前的内容
  [self.scrollView.layer renderInContext:UIGraphicsGetCurrentContext()];

  // 3. 创建文字添加到上下文
  NSString *string = @"我是水印";
  [string drawAtPoint:CGPointMake(50, 50) withAttributes:nil];

  // 3.2 添加一个图片
  UIImage *image = [UIImage imageNamed:@"current"];
  [image drawAtPoint:CGPointMake(0, 0)];

  // 4. 生成图片
  UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();

  // 5. 关闭图形上下文
  UIGraphicsEndImageContext();

  // 6. 设置图片
  UIImageView *imageView = [[UIImageView alloc] init];
  imageView.frame = CGRectMake(0, 0, scrollViewSize.width, scrollViewSize.height);

  imageView.image = newImage;

  [self.view addSubview:imageView];
  }