Method update

Update the frame rate and optionally display it on the image. :param img: Image to display FPS on. If None, just returns the FPS value. :param pos: Position to display FPS on the image. :param bgColor: Background color of the FPS text. :param textColor: Text

(self, img=None, pos=(20, 50), bgColor=(255, 0, 255),
               textColor=(255, 255, 255), scale=3, thickness=3)