def aspect(bbox):
    """
    get inverse aspect ratio a bounding box (smaller axis/larger axis)
    Parameters
    ----------
    bbox: 4-tuple
        ymin, xmin, ymax, xmax

    Returns
    -------
    aspect: scalar
        inverse aspect ratio (in 0-1)
    """

    (ymin, xmin, ymax, xmax) = bbox
    exy = ymax - ymin
    exx = xmax - xmin
    return (exy / exx) if (exx > exy) else (exx / exy)