pymrm.segmentation.wall_contact

def wall_contact(seg):
    """Whether each segment reaches each domain wall.

    Returns
    -------
    ndarray of bool, shape (n_segments, ndim_spatial, 2)
        ``out[s - 1, a, 0]`` / ``out[s - 1, a, 1]`` is ``True`` when segment
        ``s`` has cells in the first / last layer along spatial axis ``a``.

    Notes
    -----
    A fluid-side segmentation (``region="positive"``) whose segment touches no
    wall is an isolated pocket; with all-Neumann surroundings it makes the
    operator singular.  Detect them with
    ``np.flatnonzero(~wall_contact(seg).any(axis=(1, 2))) + 1``.
    """
    labels = seg.labels
    out = np.zeros((seg.n_segments, labels.ndim, 2), dtype=bool)
    for a in range(labels.ndim):
        for si, layer in enumerate((0, -1)):
            face = np.take(labels, layer, axis=a)
            present = np.unique(face)
            present = present[present > 0]
            out[present - 1, a, si] = True
    return out