Args:
        points: (nx4)x2
    Returns:
        nx4 boxes (x1y1x2y2)

def point8_to_box(points):
    """
    Args:
        points: (nx4)x2
    Returns:
        nx4 boxes (x1y1x2y2)
    """
    p = points.reshape((-1, 4, 2))
    minxy = p.min(axis=1)   # nx2
    maxxy = p.max(axis=1)   # nx2
    return np.concatenate((minxy, maxxy), axis=1)