title: How to fast convert BitmapSource to Bitmap?
body: <p>Can anyone suggest a way to convert a 2352x1726x8bit greyscale <code>BitmapSource</code> to <code>Bitmap</code> that is faster than the following taking about 600ms on a 3.2GHz P4:</p>
  
  <pre><code>    public static Bitmap toBitmap(this BitmapSource bitmapsource)
      {
          Bitmap bitmap;
          using (MemoryStream stream = new MemoryStream())
          {
              // from System.Media.BitmapImage to System.Drawing.Bitmap 
              PngBitmapEncoder enc = new PngBitmapEncoder();
              enc.Frames.Add(BitmapFrame.Create(bitmapsource));
              enc.Save(stream);
              bitmap = new System.Drawing.Bitmap(stream);
          }
          return bitmap;
      }
  </code></pre>