Rotation Transformation for Mouth and Nose Detection

Once a pair of interest peaks has a legal geometrical arrangement, we wish to test for the presence of a mouth and nose. If these structures are not present, then the detected pair of interest peaks was not a pair of eyes. Thus, we proceed by considering the next possible pair of eyes.

However, before we test for the presence of a mouth or nose, we rotate the face such that the two current possible eyes being evaluated lie on the horizontal. This simplifies the subsequent steps of detecting a mouth or a nose. We also rotate a mask representing the facial contour in a similar fashion to keep track of the interior of the facial contour. The rotated images of the face and the mask are displayed in Figure .