def approx_shoulders(upper_body_roi):
    """ Approximate the coordinates of shoulders based on upper body region of interest detection.
        Here I assume that these coordinates are more often than not located as follows:

            -> Right shoulder: 1/4 of height on Y-axis, 1/6 of width on X-axis
            -> Left shoulder: 1/4 of height on Y-axis, 5/6 of width on X-axis

        :param upper_body_roi: rectangle region of interest as matrix
        :return: 2 sets of coordinates for shoulder positions
    """
    height = upper_body_roi.shape[0]; width = upper_body_roi.shape[1]
    return (int(width / 6), int((height / 4) * 3)), (int((width / 6) * 5), int((height / 4) * 3))