title: Add a border to a QPixmap
body: <p>I load a QPixmap from a file. I want to add a border around the QPixmap, say 4px white on each side.</p>
  
  <p>What is the fastest way to do this? Do I have to create a second larger QPixmap and draw the first into the second or is there some way to extend the existing one without scaling (I've noticed that there is a <code>QPixmap::transformed()</code> but don't know if this is suitable in my case.</p>