MonoTouch screen capture in c# code

In a previous post I said that if you capture a screenshot of your application's final 'state' (say in WillTerminate) and save it as Default.png then it would be used as the 'splash screen' next time the application starts (the built-in iPhone apps like Mail seem to do this by zooming in/out with a screen capture of their last state).

The code below takes a screenshot, and was supposed to overwrite the Default.png you have in your MonoTouch application root (eg. iSOFlair.app/) and become the new splash screen. In order to 'test' this theory I had to write the code below and place it in UIViewController subclasses that I wanted to 'capture'.

Anyway, here's the code... not sure what other uses it might have?

/// <summary>
/// Capture a copy of the current View and:
/// * re-display in a UIImage control
/// * save to the Photos collection
/// * save to disk in the application's Documents folder
/// </summary>
public void ScreenCapture()
{
   var documentsDirectory = Environment.GetFolderPath
                                  (Environment.SpecialFolder.Personal);

   Console.WriteLine("start capture of frame: " + this.View.Frame.Size);
   UIGraphics.BeginImageContext(View.Frame.Size); 
   var ctx = UIGraphics.GetCurrentContext();
   if (ctx != null)
   {
      View.Layer.RenderInContext(ctx);
      UIImage img = UIGraphics.GetImageFromCurrentImageContext();
      UIGraphics.EndImageContext();
  
      // Set to display in a UIImage control _on_ the view
      imageLogo.Image = img;
  
      // Save to Photos
      img.SaveToPhotosAlbum(
         (sender, args)=>{Console.WriteLine("image saved to Photos");}
      );
  
      // Save to application's Documents folder
      string png = Path.Combine (documentsDirectory, "Screenshot.png");
      // HACK: overwrite the splash screen. iSOFlair is the application name
      //string png = Path.Combine (documentsDirectory, "../iSOFlair.app/Default.png");
      NSData imgData = img.AsPNG();
      NSError err = null;
      if (imgData.Save(png, false, out err))
      {
         Console.WriteLine("saved as " + png);
      } else {
         Console.WriteLine("NOT saved as" + png + 
                            " because" + err.LocalizedDescription);
      }
   }
   else
   {
      Console.WriteLine("ctx null - doesn't seem to happen");
   }
}

Now your MonoTouch iPhone app would appear to "startup" much faster :) There is still a bit of a trick with the View.Frame.Size - doesn't take the status bar into account - which I will try to fix up in future. UPDATE: Tested in Simulator - works fine - but doesn't appear to work on the Device :-(.

Here is a useful ObjectiveC image tricks post that was helpful.

p.s. for those who don't already know - as a user you can always take a screen capture of the current display by pressing the Home and Power buttons at the same time... a new file will be created in your Photos : Camera Roll.