'Generator for stepping through a sequence.'

def track(self):

    for i in range(len(self.imnames)):
        if (self.features == []):
            self.detect_points()
        else:
            self.track_points()
        f = array(self.features).reshape((-1), 2)
        im = cv2.cvtColor(self.image, cv2.COLOR_BGR2RGB)
        (yield (im, f))
