Tracking hand gestures in real time

Hand gestures are analyzed by the HandGestureRecognition class, especially by its recognize method. This class starts off with a few parameter initializations, which will be explained and used later:

class HandGestureRecognition:
    def __init__(self):
        # maximum depth deviation for a pixel to be considered # within range
        self.abs_depth_dev = 14

        # cut-off angle (deg): everything below this is a convexity 
        # point that belongs to two extended fingers
        self.thresh_deg = 80.0

The recognize method is where the real magic takes place. This method handles the entire process flow, from the raw grayscale image all the way to a recognized hand gesture. It implements the following procedure:

1. It extracts the user's hand region by analyzing the depth map (img_gray) and returning a hand region mask (segment):

   def recognize(self, img_gray):
       segment = self._segment_arm(img_gray)

2. It performs contour analysis on the hand region...