Let us start with image rotation. As mentioned a while back, the aim of rotating faces is to ensure that all the images have faces that are approximately straight (not tilted to the left or right). If you look at the sample images, you will notice that the face of George W. Bush is tilted slightly to the (the viewer's) left.
On the other hand, Tom Cruise's face has a tilt in the opposite direction-to the right:
We would ideally want all faces to be absolutely straight-as is the case with Kalpana Chawla:
How do we go about doing that? ...