Question

如何获取UIScrollView可见区域的1：1屏幕截图？内容可能比UIScrollView边界更大或更小，也可能是半隐藏（我已经为较小的内容实现了自定义滚动，所以它不在左上角）。我在模拟器上取得了预期的结果，但在设备本身上却没有：

-(UIImage *)imageFromCombinedContext:(UIView *)background {
      UIImage *image;
      CGRect vis = background.bounds;
      CGSize size = vis.size;
      UIGraphicsBeginImageContext(size);
      [background.layer affineTransform];
      [background.layer renderInontext:UIGraphicsGetCurrentContext()];
      image = UIGraphicsGetImageFromCurrentImageContext();
      UIGraphicsEndImageContext();
      CGImageRef imref = CGImageCreateWithImageInRect([image CGImage], vis);
      image = [UIImage imageWithCGImage:imref];
      CGImageRelease(imref);
      return image;
}

Answer 1

另一种方法是使用contentOffset来调整图层的可见区域，并仅捕获当前可见的UIScrollView区域。

UIScrollView *contentScrollView;....//scrollview instance

UIGraphicsBeginImageContextWithOptions(contentScrollView.bounds.size, 
                                       YES, 
                                       [UIScreen mainScreen].scale);

//this is the key
CGPoint offset=contentScrollView.contentOffset;
CGContextTranslateCTM(UIGraphicsGetCurrentContext(), -offset.x, -offset.y); 

[contentScrollView.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage *visibleScrollViewImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

干杯：）

Answer 2

Swd版本的Abduliam Rehmanius回答。

func screenshot() -> UIImage {

        UIGraphicsBeginImageContextWithOptions(self.scrollCrop.bounds.size, true, UIScreen.mainScreen().scale);
        //this is the key
        let offset:CGPoint = self.scrollCrop.contentOffset;
        CGContextTranslateCTM(UIGraphicsGetCurrentContext(), -offset.x, -offset.y);
        self.scrollCrop.layer.renderInContext(UIGraphicsGetCurrentContext()!);
        let visibleScrollViewImage: UIImage = UIGraphicsGetImageFromCurrentImageContext();
        UIGraphicsEndImageContext();
        return visibleScrollViewImage;
    }

Swift 4版本：

func screenshot() -> UIImage {
UIGraphicsBeginImageContextWithOptions(self.scrollCrop.bounds.size, false, UIScreen.main.scale)
        let offset = self.scrollCrop.contentOffset
        let thisContext = UIGraphicsGetCurrentContext()
        thisContext?.translateBy(x: -offset.x, y: -offset.y)
        self.scrollCrop.layer.render(in: thisContext!)
        let visibleScrollViewImage = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
return visibleScrollViewImage
}

Answer 3

我自己找到了一个解决方案 - 我截取了整个视图的截图，然后将其裁剪为UIScrollView框架的大小和位置。

-(UIImage *)imageFromCombinedContext:(UIView *)background 
{
      UIImage *image;
      CGSize size = self.view.frame.size;
      UIGraphicsBeginImageContext(size);
      [background.layer affineTransform];
      [self.view.layer.layer renderInContext:UIGraphicsGetCurrentContext()];
      image = UIGraphicsGetImageFromCurrentImageContext();
      UIGraphicsEndImageContext();
      CGImageRef imgRef = CGImageCreateWithImageInRect([image CGImage],background.frame);
      image = [UIImage imageWithCGImage:imref];
      CGImageRelease(imref);
      return image;
}

Answer 4

Jeffery Sun有正确的答案。只需将滚动视图放在另一个视图中即可。获取容器视图以在上下文中呈现。完成。

在下面的代码中，cropView包含要捕获的滚动视图。解决方案就是这么简单。

正如我理解这个问题以及为什么我找到这个页面，滚动视图的整个内容都不是必需的 - 只是可见部分。

func captureCrop() -> UIImage {
    UIGraphicsBeginImageContextWithOptions(self.cropView.frame.size, true, 0.0)
    self.cropView.layer.renderInContext(UIGraphicsGetCurrentContext())
    let image = UIGraphicsGetImageFromCurrentImageContext()
    UIGraphicsEndImageContext()
    return image;
}

Answer 5

Swift 4版本的Abduliam Rehmanius用UIScrollView extension作为翻译回答，没有慢速裁剪

extension UIScrollView {

    var snapshotVisibleArea: UIImage? {
        UIGraphicsBeginImageContext(bounds.size)
        UIGraphicsGetCurrentContext()?.translateBy(x: -contentOffset.x, y: -contentOffset.y)
        layer.render(in: UIGraphicsGetCurrentContext()!)
        let image = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        return image
    }
}

Answer 6

@Abduliam Rehmanius的回答表现不佳，因为如果UIScrollView包含大内容区域，我们将绘制整个内容区域（甚至在可见边界之外）。 @ Concuror的答案有一个问题，即它还会绘制UIScrollView之上的任何内容。

我的解决方案是将UIScrollView置于名为UIView的{{1}}内，并使用相同的边界，然后呈现containerView：

containerView

Answer 7

Swift 3.0：

 func captureScreen() -> UIImage? {
    UIGraphicsBeginImageContextWithOptions(self.yourScrollViewName.bounds.size, true, UIScreen.main.scale)
    let offset:CGPoint = self.yourScrollViewName.contentOffset;
    UIGraphicsGetCurrentContext()!.translateBy(x: -offset.x, y: -offset.y);
    self.yourScrollViewName.layer.render(in: UIGraphicsGetCurrentContext()!)
    let image = UIGraphicsGetImageFromCurrentImageContext()
    UIGraphicsEndImageContext()
    return image
}

并将其用作：让Image = captureScreen（）

Answer 8

在@Concuror代码

上更新swift 3 +，4

func getImage(fromCombinedContext background: UIView) -> UIImage {
        var image: UIImage?
        let size: CGSize = view.frame.size
        UIGraphicsBeginImageContext(size)
        background.layer.affineTransform()
        view.layer.render(in: UIGraphicsGetCurrentContext()!)
        image = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        let imgRef = image?.cgImage?.cropping(to: background.frame)
        image = UIImage(cgImage: imgRef!)
        // CGImageRelease(imgRef!) // Removing on Swift - 'CGImageRelease' is unavailable: Core Foundation objects are automatically memory managed
        return image ?? UIImage()
    }

如何截取UIScrollView可视区域的截图？

8 个答案: