Question

I am using EmguCV in WPF and i found this example tp capture image , I want to use bs1 in my some other method Method3(), but i am getting error that object belong to some other thread, anyone has any idea what is the problem ? bs1 is after all a global variable

  BitmapSource bs1;

 private void Window_Loaded(object sender, RoutedEventArgs e)
    {
        capture = new Capture();       ///capture image

        timer = new DispatcherTimer();       // timer object
        timer.Interval = new TimeSpan(500);
        timer.Tick += new EventHandler(timer_Tick);
        timer.Start();

    }
    void timer_Tick(object sender, EventArgs e)
    {
        using (  Image<Bgr, byte> Frame = capture.QueryFrame())
        {
            if (Frame != null)
            {
                bs1 = ToBitmapSource(Frame);
webcam.Source = ToBitmapSource(Frame); // ToBitmapSource convert image to bitmapsource webcam is a picture in mainwindow
                 Frame.Save("fg.jpeg");   //this work but use lot of processing 

            }
        }
    }


public void Method3_click (...)
{
    use_of_bs1(bs1);
}


  private void use_of_bs1()
    {

        data.Text = "waiting...";

        System.Threading.ThreadPool.QueueUserWorkItem(Startwork);
    }


    private void Startwork(object state)
    {

        try
        {
            _work = _worker.bs1_analysis(bs1);      // it is where bs1 giving thread errorbs1_analysis is library function
        }
        catch (Exception ex)
        {
            Dispatcher.BeginInvoke(new ShowworkInformationDelegate(ShowworkInformation));
            MessageBox.Show(ex.Message, "Error", MessageBoxButton.OK, MessageBoxImage.Error);
            return;
        }
        Dispatcher.BeginInvoke(new ShowWorkInformationDelegate(ShowWorkInformation));

    }

/// ToBitmapsource function is

public static BitmapSource ToBitmapSource(Emgu.CV.IImage image)
    {
        using (System.Drawing.Bitmap source = image.Bitmap)
        {
            IntPtr ptr = source.GetHbitmap();
            BitmapSource bs = System.Windows.Interop.Imaging.CreateBitmapSourceFromHBitmap(ptr, IntPtr.Zero, Int32Rect.Empty, System.Windows.Media.Imaging.BitmapSizeOptions.FromEmptyOptions());
            DeleteObject(ptr);
            return bs;
        }
    }

Answer 1

If you create a wpf resource and want to use it on a different thread, you can call Freeze() on the object before passing it on. That will make it immutable and legal to use on another thread.