How to capture a full page screenshot of WKWebview? - ios

Question

I can capture all content screenshot of UIWebView by adjust frame of UIScrollView of UIWebView. However, I can't capture all content screenshot of WKWebView by the same method.
The method I used for capture UIWebView as follow:
backup frame and superview of webview.scrollView
create a new container view as webview.scrollView's superview
adjust frame of new container view and webview.scrollView. frame is same to webview.scrollView.contentSize
draw by renderInContext or drawViewHierarchyInRect
However, this method will capture a white screenshot of WKWebview. It doesn't work!
I had print all level of WKWebView, then I found a UIView(WKContentView)'s size is same to contentView, you can found this view by this level:
WKWebView
WKScrollView
WKContentView(size is same to contentView)
I also had try to capture by WKContentView, then I found only visible view could be captured.
Anyway, Anyone could tell me how to capture a full page content screenshot of WKWebView?

Answer 1

Please refer to this answer
iOS 11.0 and above, Apple has provided following API to capture snapshot of WKWebView.
#available(iOS 11.0, *)
open func takeSnapshot(with snapshotConfiguration: WKSnapshotConfiguration?, completionHandler: #escaping (UIImage?, Error?) -> Swift.Void)

Answer 2

Swift 3, Xcode 8
func takeScreenshot() -> UIImage? {
let currentSize = webView.frame.size
let currentOffset = webView.scrollView.contentOffset
webView.frame.size = webView.scrollView.contentSize
webView.scrollView.setContentOffset(CGPoint.zero, animated: false)
let rect = CGRect(x: 0, y: 0, width: webView.bounds.size.width, height: webView.bounds.size.height)
UIGraphicsBeginImageContextWithOptions(rect.size, false, UIScreen.main.scale)
webView.drawHierarchy(in: rect, afterScreenUpdates: true)
let image = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
webView.frame.size = currentSize
webView.scrollView.setContentOffset(currentOffset, animated: false)
return image
}

Answer 3

Swift 3, Xcode 9:
I created an extension to achieve this. Hope this helps you.
extension WKWebView{
private func stageWebViewForScreenshot() {
let _scrollView = self.scrollView
let pageSize = _scrollView.contentSize;
let currentOffset = _scrollView.contentOffset
let horizontalLimit = CGFloat(ceil(pageSize.width/_scrollView.frame.size.width))
let verticalLimit = CGFloat(ceil(pageSize.height/_scrollView.frame.size.height))
for i in stride(from: 0, to: verticalLimit, by: 1.0) {
for j in stride(from: 0, to: horizontalLimit, by: 1.0) {
_scrollView.scrollRectToVisible(CGRect(x: _scrollView.frame.size.width * j, y: _scrollView.frame.size.height * i, width: _scrollView.frame.size.width, height: _scrollView.frame.size.height), animated: true)
RunLoop.main.run(until: Date.init(timeIntervalSinceNow: 1.0))
}
}
_scrollView.setContentOffset(currentOffset, animated: false)
}
func fullLengthScreenshot(_ completionBlock: ((UIImage) -> Void)?) {
// First stage the web view so that all resources are downloaded.
stageWebViewForScreenshot()
let _scrollView = self.scrollView
// Save the current bounds
let tmp = self.bounds
let tmpFrame = self.frame
let currentOffset = _scrollView.contentOffset
// Leave main thread alone for some time to let WKWebview render its contents / run its JS to load stuffs.
mainDispatchAfter(2.0) {
// Re evaluate the size of the webview
let pageSize = _scrollView.contentSize
UIGraphicsBeginImageContext(pageSize)
self.bounds = CGRect(x: self.bounds.origin.x, y: self.bounds.origin.y, width: pageSize.width, height: pageSize.height)
self.frame = CGRect(x: self.frame.origin.x, y: self.frame.origin.y, width: pageSize.width, height: pageSize.height)
// Wait few seconds until the resources are loaded
RunLoop.main.run(until: Date.init(timeIntervalSinceNow: 0.5))
self.layer.render(in: UIGraphicsGetCurrentContext()!)
let image: UIImage = UIGraphicsGetImageFromCurrentImageContext()!
UIGraphicsEndImageContext()
// reset Frame of view to origin
self.bounds = tmp
self.frame = tmpFrame
_scrollView.setContentOffset(currentOffset, animated: false)
completionBlock?(image)
}
}
}

Answer 4

The key here is to let capture after webkit be allowed time to render after it is given a new frame. I tried didFinishLoading calback and WKWebView's wkWebView.takeSnapshot, but did not work.
So I introduced an a delay for the screenshot:
func createImage(webView: WKWebView, completion: #escaping (UIImage?) -> ()) {
// save the original size to restore
let originalFrame = webView.frame
let originalConstraints = webView.constraints
let originalScrollViewOffset = webView.scrollView.contentOffset
let newSize = webView.scrollView.contentSize
// remove any constraints for the web view, and set the size
// to be size of the content size (will be restored later)
webView.removeConstraints(originalConstraints)
webView.translatesAutoresizingMaskIntoConstraints = true
webView.frame = CGRect(origin: .zero, size: newSize)
webView.scrollView.contentOffset = .zero
// wait for a while for the webview to render in the newly set frame
DispatchQueue.main.asyncAfter(deadline: .now() + 4.0) {
defer {
UIGraphicsEndImageContext()
}
UIGraphicsBeginImageContextWithOptions(newSize, false, 0)
if let context = UIGraphicsGetCurrentContext() {
// render the scroll view's layer
webView.scrollView.layer.render(in: context)
// restore the original state
webView.frame = originalFrame
webView.translatesAutoresizingMaskIntoConstraints = false
webView.addConstraints(originalConstraints)
webView.scrollView.contentOffset = originalScrollViewOffset
if let image = UIGraphicsGetImageFromCurrentImageContext() {
completion(image)
} else {
completion(nil)
}
}
}
}
Result:

Answer 5

- xcode 10 & swift 4.2 -
Use this;
// this is the button which takes the screenshot
#IBAction func snapShot(_ sender: Any) {
captureScreenshot()
}
// this is the function which is the handle screenshot functionality.
func captureScreenshot(){
let layer = UIApplication.shared.keyWindow!.layer
let scale = UIScreen.main.scale
// Creates UIImage of same size as view
UIGraphicsBeginImageContextWithOptions(layer.frame.size, false, scale);
layer.render(in: UIGraphicsGetCurrentContext()!)
let screenshot = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
// THIS IS TO SAVE SCREENSHOT TO PHOTOS
UIImageWriteToSavedPhotosAlbum(screenshot!, nil, nil, nil)
}
and you must add these keys in your info.plist;
key value = "Privacy - Photo Library Additions Usage Description" ,
key value = Privacy - Photo Library Usage Description

Answer 6

Here is an iOS 11+ example for snapshotting the WKWebView without the need of any delays to render the content.
The key is to make sure that you dont receive a blank snapshot. Initially we had issues with the output image being blank and having to introduce a delay to have the web content in the output image. I see the solution with the delay in many posts and I would recommend to not use it because it is an unnecessarily unreliable and unperformant solution. The important solution for us was to set the rect of WKSnapshotConfiguration and to use the JavaScript functions to wait for the rendering and also receiving the correct width and height.
Setting up the WKWebView:
// Important: You can set a width here which will also be reflected in the width of the snapshot later
let webView = WKWebView(frame: .zero)
webView.configuration.dataDetectorTypes = []
webView.navigationDelegate = self
webView.scrollView.contentInsetAdjustmentBehavior = .never
webView.loadHTMLString(htmlString, baseURL: Bundle.main.resourceURL)
Capturing the snapshot:
func webView(
_ webView: WKWebView,
didFinish navigation: WKNavigation!
) {
// Wait for the page to be rendered completely and get the final size from javascript
webView.evaluateJavaScript("document.readyState", completionHandler: { [weak self] (readyState, readyStateError) in
webView.evaluateJavaScript("document.documentElement.scrollWidth", completionHandler: {(contentWidth, widthError) in
webView.evaluateJavaScript("document.documentElement.scrollHeight", completionHandler: { (contentHeight, heightError) in
guard readyState != nil,
let contentHeight = contentHeight as? CGFloat,
let contentWidth = contentWidth as? CGFloat else {
[Potential error handling...]
return
}
let rect = CGRect(
x: 0,
y: 0,
width: contentWidth,
height: contentHeight
)
let configuration = WKSnapshotConfiguration()
configuration.rect = rect
if #available(iOS 13.0, *) {
configuration.afterScreenUpdates = true
}
webView.takeSnapshot(with: configuration) { (snapshotImage, error) in
guard let snapshotImage = snapshotImage else {
[Potential error handling...]
}
[Do something with the image]
}
})
})
})
}

Answer 7

UPDATE: Not sure why Jason is sticking this answer all over the net. IT DOES NOT solve the problem of HOW to Screenshot the Full WKWebView content... including that off the screen.
Try this:
func snapshot() -> UIImage {
UIGraphicsBeginImageContextWithOptions(self.webView.bounds.size, true, 0);
self.webView.drawViewHierarchyInRect(self.webView.bounds, afterScreenUpdates: true);
let snapshotImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
UIImageWriteToSavedPhotosAlbum(snapshotImage, nil, nil, nil)
return snapshotImage
}
The image will automatically save into the iOS Camera Roll (by UIImageWriteToSavedPhotosAlbum()).