Screenshot of current UIView distorts and stretches the UIView at UIView.DrawViewHierarchy

Question

I'm creating a screenshot of a UIView currently displayed. I faced with an issue when controls are distorted and stretched for a moment (0.2-0.5 sec) during this process. It is reproduced for iPhone 6, 6+ ONLY.

my simple code is here (Xamarin.iOS):

public UIImage CreateScreenshotImage()
{
    UIView rootView = UIApplication.SharedApplication.KeyWindow.RootViewController.View;
    if (rootView != null)
    {
        var bounds = rootView.Bounds;
        UIGraphics.BeginImageContextWithOptions(bounds.Size, false, 0);
        **//here distortion starts, I can clearly see it in the DEBUG mode**
        rootView.DrawViewHierarchy(bounds, true); 
        var screenshotImage = UIGraphics.GetImageFromCurrentImageContext();
        UIGraphics.EndImageContext();
        return screenshotImage;
     }
     return null;
}

I don't believe it is related to Xamarin so it should be the same issue for native iOS app as well.

What could be the reason?

Answer 1

Try with this:

public static class UIViewScreenshot
{
    public static UIImage Screenshot(this UIView view, bool optimized = true)
    {
        if (optimized)
        {
            // take screenshot of the view
            if (view.GetType ().Name == "MKMapView") {
                if (float.Parse(UIDevice.CurrentDevice.SystemVersion) >= 6.0) {

                    // in iOS6, there is no problem using a non-retina screenshot in a retina display screen
                    UIGraphics.BeginImageContextWithOptions (view.Frame.Size, false, 1.0f);

                } else {

                    // if the view is a mapview in iOS5.0 and below, screenshot has to take the screen scale into consideration
                    // else, the screen shot in retina display devices will be of a less detail map (note, it is not the size of the screenshot, but it is the level of detail of the screenshot
                    UIGraphics.BeginImageContextWithOptions (view.Frame.Size, false, 1.0f);
                }
            } else {
                // for performance consideration, everything else other than mapview will use a lower quality screenshot
                UIGraphics.BeginImageContext (view.Frame.Size); 
            }

        } else
        {
            UIGraphics.BeginImageContextWithOptions (view.Frame.Size, false, 0.0f);
        }


        var context = UIGraphics.GetCurrentContext ();

        if (context == null)
        {
            Console.WriteLine("UIGraphicsGetCurrentContext() is nil. You may have a UIView with CGRectZero");
            return null;
        }
        else
        {
            view.Layer.RenderInContext (context);

            var screenshot = UIGraphics.GetImageFromCurrentImageContext ();
            UIGraphics.EndImageContext();

            return screenshot;
        }
    }
}