Convert System.Windows.Controls.Image to System.Drawing.Image HOW

Cannot implicitly convert type 'System.Windows.Controls.Image' to 'System.Drawing.Image'

private void button4_Click(object sender, EventArgs e){
     GimageSearchClient client = new GimageSearchClient("http://www.google.com");
            IList<IImageResult> results;
            IAsyncResult result = client.BeginSearch(
                textBox1.Text.Trim(),  //param1
                10, //param2
                ((arResult) => //param3
                {
                    results = client.EndSearch(arResult);
                    Dispatcher.CurrentDispatcher.BeginInvoke(DispatcherPriority.Send,
                        (Action<IList<IImageResult>>)(async (data) =>
                         {
                             Random r = new Random();
                             Image img = new Image
                             {
                                 Source = await DownloadImage(results[r.Next(results.Count)].TbImage.Url),
                                 Stretch = Stretch.UniformToFill,
                                 StretchDirection = StretchDirection.DownOnly,
                             };
                                                          
                             //////// img add to Picturebox HOW ? 

                         }), null);
                }),
                null //param4 
                );
        }