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? Keep in mind; we need a system that should accomplish the following:
If the face is tilted, rotate it so that the tilt is nullified.
For faces that are already straight, the system should leave that as it is.
Since our aim is to reach a state where the face has zero-tilt, let's try to emulate some properties that such a face possesses so that, given any facial image, we can devise a procedure to reach there. The mechanism that we propose goes...