After a face has been detected, we might want to preprocess the extracted head region before applying classification to it. Although the face cascade is fairly accurate, for the recognition, it is important that all the faces are upright and centered on the image.
Here is what we want to accomplish:
Image credit—Lenna.png by Conor Lawless is licensed under CC BY 2.0
As you can see from the preceding screenshot, as this is not a passport photo, the model has her head slightly tilted to the side while looking over her shoulder. The facial region, as extracted by the face cascade, is shown in the middle thumbnail ...
