title: How do you composite an image onto another image with PIL in Python?
body: <p>I need to take an image and place it onto a new, generated white background in order for it to be converted into a downloadable desktop wallpaper. So the process would go:</p>
  
  <ol>
  <li>Generate new, all white image with 1440x900 dimensions</li>
  <li>Place existing image on top, centered</li>
  <li>Save as single image</li>
  </ol>
  
  <p>In PIL, I see the <code>ImageDraw</code> object, but nothing indicates it can draw existing image data onto another image. Suggestions or links anyone can recommend?</p>