def get_biggest_face(array_of_faces):
    """
    :param array_of_faces: array of faces returned from detector.detectMultiScale()
    :return: a 1x4 array containing the face with the biggest area (width*height)
    """
    largest_area = 0
    largest_face = None
    for face in array_of_faces:
        area = face[2] * face[3]  # width * height
        if area > largest_area:
            largest_area = area
            largest_face = face
    return [largest_face]