Replaces superpixel labels with their mean value.
    inputs:
        suppxls ... image with suppxls labels, ndarray
        suppxl_intens ... vector with suppxls mean intensities
        im ... input image
    outputs:
        suppxl_ints_im ... image with suppxls mean intensities, ndarray same shape as suppxls

def suppxl_ints2im(suppxls, suppxl_ints=None, im=None):
    """Replaces superpixel labels with their mean value.
    inputs:
        suppxls ... image with suppxls labels, ndarray
        suppxl_intens ... vector with suppxls mean intensities
        im ... input image
    outputs:
        suppxl_ints_im ... image with suppxls mean intensities, ndarray same shape as suppxls
    """

    suppxl_ints_im = np.zeros(suppxls.shape)

    if suppxl_ints is None and im is not None:
        suppxl_ints = get_superpxl_intensities(im, suppxls)

    for i in np.unique(suppxls):
        sup = suppxls == i
        val = suppxl_ints[i]
        suppxl_ints_im[np.nonzero(sup)] = val

    return suppxl_ints_im