title: Take a screenshot of a WPF window with the predefined image size without losing quality
body: <p>When I take a screenshot of a current WPF window, the image resolution is that of my monitor (if the app is maximized), which is ok. However, if I was to print that image to a much bigger format, the image would look blurry. I found the way to capture the current window, and save it as a png file, but it's not doing the trick. The image is saved with the resolution I set, but the actual wpf window takes only a small portion of the saved image. Example is taken from:</p>
  
  <p><a href="http://blogs.msdn.com/b/saveenr/archive/2008/09/18/wpf-xaml-saving-a-window-or-canvas-as-a-png-bitmap.aspx" rel="noreferrer">http://blogs.msdn.com/b/saveenr/archive/2008/09/18/wpf-xaml-saving-a-window-or-canvas-as-a-png-bitmap.aspx</a></p>
  
  <pre><code>        var screen = System.Windows.Application.Current.Windows.OfType&lt;Window&gt;().SingleOrDefault(x =&gt; x.IsActive);
  
          var rtb = new RenderTargetBitmap(4000, 4000, 96, 96, PixelFormats.Pbgra32);
  
          rtb.Render(screen);
  
          var enc = new System.Windows.Media.Imaging.PngBitmapEncoder();
          enc.Frames.Add(System.Windows.Media.Imaging.BitmapFrame.Create(rtb));
  
          using (var stm = System.IO.File.Create("ScreenShot.png"))
          {
              enc.Save(stm);
              using (Image img = Image.FromStream(stm))
              {
                  Rectangle dest = new Rectangle(0, 0, 6000, 4000);
  
                  using (Graphics imgG = Graphics.FromImage(img))
                  {
                      imgG.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
                      imgG.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
                      imgG.DrawImage(img, dest);
                  }
  
                  img.Save("NewScreenShot.png");
              }
          }
  </code></pre>
  
  <p>So basically, I'd like to capture the screenshot with the resolution of 4000 x 4000, if that's possible, without losing quality. 
  The above code produces an image of 4000 x 4000, however the screenshot only takes a small portion of it, its original resolution.</p>