private void CaptureButton_Click(object sender, RoutedEventArgs e)
        {
            // save coordinates of 'content grid'
            System.Windows.Point locationFromScreen =
                ContentGrid.PointToScreen(new System.Windows.Point(0, 0));
            contentGrid_X      = locationFromScreen.X;
            contentGrid_Y      = locationFromScreen.Y;
            contentGrid_Width  = ContentGrid.ActualWidth;
            contentGrid_Height = ContentGrid.ActualHeight;

            // hide window
            this.WindowState = WindowState.Minimized;

            // wait some seconds
            timer          = new DispatcherTimer();
            timer.Interval = TimeSpan.FromSeconds(2);

            timer.Tick += (paramSender, paramArgs) =>
            {
                timer.Stop();

                Thread t = new Thread(new ThreadStart(StartProcessing));
                Stop = false;
                t.Start();
            };
            timer.Start();
        }