Getting a screenshot of a UIScrollView, including offscreen parts

I have a UIScrollView decendent that implements a takeScreenshot method that looks like this:

-(void)takeScreenshot {  
  CGRect contextRect  = CGRectMake(0, 0, 768, 1004);
  UIGraphicsBeginImageContext(contextRect.size);    
  [self.layer renderInContext:UIGraphicsGetCurrentContext()];
  UIImage *viewImage = UIGraphicsGetImageFromCurrentImageContext();
  UIGraphicsEndImageContext();

  // do something with the viewImage here.
}

This basically moves to the top of the scroll view, and takes a screenshot of the visible area. It works fine when the iPad is oriented portrait, but when it's in landscape the bottom of the image is cut off (as the height of the visible area is only 748, not 1004).

Is it possible to get a snapshot of the UIScrollView, including areas not on screen? Or do I need to scroll the view down, take a second photo and stitch them together?

Here is code that works ...

- (IBAction) renderScrollViewToImage
{
    UIImage* image = nil;

    UIGraphicsBeginImageContext(_scrollView.contentSize);
    {
        CGPoint savedContentOffset = _scrollView.contentOffset;
        CGRect savedFrame = _scrollView.frame;

        _scrollView.contentOffset = CGPointZero;
        _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) {
        [UIImagePNGRepresentation(image) writeToFile: @"/tmp/test.png" atomically: YES];
        system("open /tmp/test.png");
    }
}

The last few lines simply write the image to /tmp/test.png and then opens it in Preview.app. This obviously only works on in the Simulator :-)

Complete project in the ScrollViewScreenShot Github Repository

For me, the currently accepted answer from Stefan Arentz didn't work.

I had to implement this on iOS 8 and above, and tested on the iPhone. The accepted answer just renders the visible part of a scroll view, while the rest of image remains blank.

I tried fixing this using drawViewHierarchyInRect - no luck. Depending on afterScreenUpdates being true or false I got stretched part of image or only part of the contents.

The only way I've found to achieve correct snapshotting of a UIScrollView's entire contents is to add it to another temporary view and then render it.

Sample code is below (scrollview is outlet in my VC)

func getImageOfScrollView() -> UIImage {
    var image = UIImage()

    UIGraphicsBeginImageContextWithOptions(self.scrollView.contentSize, false, UIScreen.mainScreen().scale)

    // save initial values
    let savedContentOffset = self.scrollView.contentOffset
    let savedFrame = self.scrollView.frame
    let savedBackgroundColor = self.scrollView.backgroundColor

    // reset offset to top left point
    self.scrollView.contentOffset = CGPointZero
    // set frame to content size
    self.scrollView.frame = CGRectMake(0, 0, self.scrollView.contentSize.width, self.scrollView.contentSize.height)
    // remove background
    self.scrollView.backgroundColor = UIColor.clearColor()

    // make temp view with scroll view content size
    // a workaround for issue when image on ipad was drawn incorrectly
    let tempView = UIView(frame: CGRectMake(0, 0, self.scrollView.contentSize.width, self.scrollView.contentSize.height))

    // save superview
    let tempSuperView = self.scrollView.superview
    // remove scrollView from old superview
    self.scrollView.removeFromSuperview()
    // and add to tempView
    tempView.addSubview(self.scrollView)

    // render view
    // drawViewHierarchyInRect not working correctly
    tempView.layer.renderInContext(UIGraphicsGetCurrentContext())
    // and get image
    image = UIGraphicsGetImageFromCurrentImageContext()

    // and return everything back
    tempView.subviews[0].removeFromSuperview()
    tempSuperView?.addSubview(self.scrollView)

    // restore saved settings
    self.scrollView.contentOffset = savedContentOffset
    self.scrollView.frame = savedFrame
    self.scrollView.backgroundColor = savedBackgroundColor

    UIGraphicsEndImageContext()

    return image
}

Working Example of UIView Extension with handling for UIScrollView:

extension UIView {
    func screenshot() -> UIImage {

            if(self is UIScrollView) {
                let scrollView = self as! UIScrollView

                let savedContentOffset = scrollView.contentOffset
                let savedFrame = scrollView.frame

                UIGraphicsBeginImageContext(scrollView.contentSize)
                scrollView.contentOffset = .zero
                self.frame = CGRect(x: 0, y: 0, width: scrollView.contentSize.width, height: scrollView.contentSize.height)
                self.layer.render(in: UIGraphicsGetCurrentContext()!)
                let image = UIGraphicsGetImageFromCurrentImageContext()
                UIGraphicsEndImageContext();

                scrollView.contentOffset = savedContentOffset
                scrollView.frame = savedFrame

                return image!
            }

            UIGraphicsBeginImageContext(self.bounds.size)
            self.layer.render(in: UIGraphicsGetCurrentContext()!)
            let image = UIGraphicsGetImageFromCurrentImageContext()
            UIGraphicsEndImageContext()
            return image!

        }
}

I took this solution from @Roopesh Mittal's answer and made it safer/cleaner.

Swift 5 compatible

fileprivate extension UIScrollView {
    func screenshot() -> UIImage? {
        let savedContentOffset = contentOffset
        let savedFrame = frame

        UIGraphicsBeginImageContext(contentSize)
        contentOffset = .zero
        frame = CGRect(x: 0, y: 0, width: contentSize.width, height: contentSize.height)

        guard let context = UIGraphicsGetCurrentContext() else { return nil }

        layer.render(in: context)
        let image = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext();

        contentOffset = savedContentOffset
        frame = savedFrame

        return image
    }
}

A refined Swift 4.x/5.0 version, based on @RyanG 's answer:

fileprivate extension UIScrollView {
    func screenshot() -> UIImage? {
        // begin image context
        UIGraphicsBeginImageContextWithOptions(contentSize, false, 0.0)
        // save the orginal offset & frame 
        let savedContentOffset = contentOffset
        let savedFrame = frame
        // end ctx, restore offset & frame before returning
        defer {
            UIGraphicsEndImageContext()
            contentOffset = savedContentOffset
            frame = savedFrame
        }
        // change the offset & frame so as to include all content
        contentOffset = .zero
        frame = CGRect(x: 0, y: 0, width: contentSize.width, height: contentSize.height)
        guard let ctx = UIGraphicsGetCurrentContext() else {
            return nil
        }
        layer.render(in: ctx)
        let image = UIGraphicsGetImageFromCurrentImageContext()

        return image
    }
}