title: Silverlight: converting WriteableBitmap to stream
body: <p>Given a WriteableBitmap, how can I save the bitmap back into an image stream (JPG or BMP)?</p>
  
  <p>My scenario is:</p>
  
  <ol>
  <li>Show OpenFileDialog, let user select image</li>
  <li>Load image into WriteableBitmap</li>
  <li>Resize image</li>
  <li>Send image stream to web service</li>
  </ol>
  
  <p>Step #4 is what I'm having trouble with. How can I go from WriteableBitmap -> Stream?</p>