randomdrake/nasa-apod-desktop — pull request #3 by milot-mirdita (2012-07-30 00:28:54+00:00)
Title: Keep the aspect ratio through ImageOps.fit

With the use of ImageOps.fit the aspect ratio of the picture isn't distorted. This cuts off (in a pretty dumb way) that is outside of the center.
A better approach might be something based on image entropy to cut out "uninteresting" parts of the images. Reddit uses a setup similar to this to make good thumbnails.