title: RenderTargetBitmap Memory Leak
body: <p>am trying to render an image with RenderTargetBitmap
  every time i create an instance from RenderTargetBitmap to render image the memory increased and when am done the memory never released 
  and this is the code :</p>
  
  <pre><code>RenderTargetBitmap rtb = new RenderTargetBitmap((int)(renderWidth * dpiX / 96.0),
                                                  (int)(renderHeight * dpiY / 96.0),
                                                  dpiX,
                                                  dpiY,
                                                  PixelFormats.Pbgra32);
      DrawingVisual dv = new DrawingVisual();
      using (DrawingContext ctx = dv.RenderOpen())
      {
         VisualBrush vb = new VisualBrush(target);
         ctx.DrawRectangle(vb, null, new System.Windows.Rect(new Point(0, 0), new Point(bounds.Width, bounds.Height)));
      }
      rtb.Render(dv);
  </code></pre>
  
  <p>please i need help
  how can i release the memory
  and thanks for all.</p>