How to convert a UIView to an image

Question

An extension on UIView should do the trick.

extension UIView {

    // Using a function since `var image` might conflict with an existing variable
    // (like on `UIImageView`)
    func asImage() -> UIImage {
        let renderer = UIGraphicsImageRenderer(bounds: bounds)
        return renderer.image { rendererContext in
            layer.render(in: rendererContext.cgContext)
        }
    }
}

Apple discourages using UIGraphicsBeginImageContext starting iOS 10 with the introduction of the P3 color gamut. UIGraphicsBeginImageContext is sRGB and 32-bit only. They introduced the new UIGraphicsImageRenderer API that is fully color managed, block-based, has subclasses for PDFs and images, and automatically manages the context lifetime. Check out WWDC16 session 205 for more details (image rendering begins around the 11:50 mark)

To be sure that it works on every device, use #available with a fallback to earlier versions of iOS:

extension UIView {

    // Using a function since `var image` might conflict with an existing variable
    // (like on `UIImageView`)
    func asImage() -> UIImage {
        if #available(iOS 10.0, *) {
            let renderer = UIGraphicsImageRenderer(bounds: bounds)
            return renderer.image { rendererContext in
                layer.render(in: rendererContext.cgContext)
            }
        } else {
            UIGraphicsBeginImageContext(self.frame.size)
            self.layer.render(in:UIGraphicsGetCurrentContext()!)
            let image = UIGraphicsGetImageFromCurrentImageContext()
            UIGraphicsEndImageContext()
            return UIImage(cgImage: image!.cgImage!)
        }
    }
}

you can use extension

extension UIImage {
    convenience init(view: UIView) {
        UIGraphicsBeginImageContext(view.frame.size)
        view.layer.render(in:UIGraphicsGetCurrentContext()!)
        let image = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        self.init(cgImage: image!.cgImage!)
    }
}

Here the swift 3/4 version :

extension UIImage {
    convenience init(view: UIView) {
        UIGraphicsBeginImageContext(view.frame.size)
        view.layer.render(in:UIGraphicsGetCurrentContext()!)
        let image = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        self.init(cgImage: image!.cgImage!)
    }
}

Convert your UIView to image by drawViewHierarchyInRect:afterScreenUpdates: which is many times faster than renderInContext

Important note: do not call this function from viewDidLoad or viewWillAppear , make sure you are capturing a view after it is it displayed /loaded fully

Obj C

     UIGraphicsBeginImageContextWithOptions(myView.bounds.size, myView.opaque, 0.0f);
     [myView drawViewHierarchyInRect:myView.bounds afterScreenUpdates:NO];
     UIImage *snapshotImageFromMyView = UIGraphicsGetImageFromCurrentImageContext();
     UIGraphicsEndImageContext();

     myImageView.image =  snapshotImageFromMyView;

Save the edited image Photo album

     UIImageWriteToSavedPhotosAlbum(snapshotImageFromMyView, nil,nil, nil);

Swift 3/4

    UIGraphicsBeginImageContextWithOptions(myView.bounds.size, myView.isOpaque, 0.0)
    myView.drawHierarchy(in: myView.bounds, afterScreenUpdates: false)
    let snapshotImageFromMyView = UIGraphicsGetImageFromCurrentImageContext()
    UIGraphicsEndImageContext()
    print(snapshotImageFromMyView)
    myImageView.image = snapshotImageFromMyView

Super easy generalization with extension , iOS11 , swift3/4

extension UIImage{
    convenience init(view: UIView) {

    UIGraphicsBeginImageContextWithOptions(view.bounds.size, view.isOpaque, 0.0)
    view.drawHierarchy(in: view.bounds, afterScreenUpdates: false)
    let image = UIGraphicsGetImageFromCurrentImageContext()
    UIGraphicsEndImageContext()
    self.init(cgImage: (image?.cgImage)!)

  }
}


Use : 
 //myView is completly loaded/visible , calling this code after only after viewDidAppear is call
 imgVV.image = UIImage.init(view: myView)
 // Simple image object
 let img =  UIImage.init(view: myView)

On iOS 10:

extension UIImage {
    convenience init(view: UIView) {
        UIGraphicsBeginImageContext(view.frame.size)
        view.layer.render(in: UIGraphicsGetCurrentContext()!)
        let image = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        self.init(cgImage: (image?.cgImage)!)
    }
}

Best practice as of iOS 10 and Swift 3

while still supporting iOS 9 and earlier still works as of iOS 13, Xcode 11.1, Swift 5.1

extension UIView {

    func asImage() -> UIImage? {
        if #available(iOS 10.0, *) {
            let renderer = UIGraphicsImageRenderer(bounds: bounds)
            return renderer.image { rendererContext in
                layer.render(in: rendererContext.cgContext)
            }
        } else {
            UIGraphicsBeginImageContextWithOptions(self.bounds.size, self.isOpaque, 0.0)
            defer { UIGraphicsEndImageContext() }
            guard let currentContext = UIGraphicsGetCurrentContext() else {
                return nil
            }
            self.layer.render(in: currentContext)
            return UIGraphicsGetImageFromCurrentImageContext()
        }
    }
}

I am unsure what the question means by:

what is the best way to save it in an app (Not camera roll)?