title: How to draw directly on bitmap (BitmapSource, WriteableBitmap) in WPF?
body: <p>In GDI+ Winforms I would do:</p>
  
  <pre><code>Bitmap b = new Bitmap(32,32);
  Graphics g = Graphics.FromImage(b); 
  //some graphics code...`
  </code></pre>
  
  <p>How to do the same thing in WPF, with a DrawingContext?</p>