def band_info(band_names, band_uris=None):
    """
    :param list band_names: names of the bands
    :param dict band_uris: mapping from names to dicts with 'path' and 'layer' specs
    """
    if band_uris is None:
        band_uris = {name: {'path': '', 'layer': name} for name in band_names}

    return {
        'image': {
            'bands': {name: band_uris[name] for name in band_names}
        }
    }