def cvtStokesToIntensity(img_stokes):
    """
    Convert stokes vector image to intensity image

    Parameters
    ----------
    img_stokes : np.ndarray, (height, width, 3)
        Stokes vector image

    Returns
    -------
    img_intensity : np.ndarray, (height, width)
        Intensity image
    """
    S0 = img_stokes[..., 0]
    return S0*0.5