Before we start implementing a high-level tracker, we should define the type of tracking result that we want to get. For many applications, it is important to estimate how objects are posed in real, 3D space. However, our application is about image manipulation. So we care more about 2D image space. An upright, frontal view of a face should occupy a roughly rectangular region in the image. Within such a region, eyes, a nose, and a mouth should occupy rough rectangular subregions. Let's open trackers.py and add a class containing the relevant data:
class Face(object):
"""Data on facial features: face, eyes, nose, mouth."""
def __init__(self):
self.faceRect = None
self.leftEyeRect = None
self.rightEyeRect = None
self.noseRect = None
self.mouthRect = None