find_trapped_clusters

Given an invasion sequence map and a set of outlets, returns a boolean mask of voxels of the displaced phase that are cut off from the outlets at some point during the invasion.

import matplotlib.pyplot as plt
import numpy as np

import porespy as ps

ps.visualization.set_mpl_style()

The arguments and their defaults are:

import inspect

inspect.signature(ps.filters.find_trapped_clusters)

<Signature (im: ArrayLike, seq: ArrayLike, outlets: ArrayLike, min_size: int = 0, conn: Literal['min', 'max'] = 'min', method: Literal['queue', 'labels'] = 'labels')>

im, seq, outlets

im is the boolean void mask, seq is an invasion-sequence map (e.g. the im_seq returned by drainage or imbibition), and outlets is a boolean mask of the cells through which the displaced phase can leave.

np.random.seed(0)
im = ps.generators.blobs(shape=[200, 200], porosity=0.65, seed=2)
im = ps.filters.fill_closed_pores(im)
inlets = ps.generators.faces(im.shape, inlet=0)
outlets = ps.generators.faces(im.shape, outlet=0)
pc = ps.filters.capillary_transform(
    im=im, sigma=0.072, theta=180, voxel_size=1e-5)
drn = ps.simulations.drainage(im=im, pc=pc, inlets=inlets)

trapped = ps.filters.find_trapped_clusters(
    im=im, seq=drn.im_seq, outlets=outlets)

fig, ax = plt.subplots(1, 2, figsize=[10, 5])
ax[0].imshow(drn.im_seq / im, origin='lower', interpolation='none')
ax[0].set_title('invasion sequence')
ax[0].axis(False)
ax[1].imshow(trapped, origin='lower', interpolation='none')
ax[1].set_title('trapped voxels')
ax[1].axis(False);

method

Two algorithms are available. 'labels' (default) uses scipy.ndimage.label at each sequence step and is faster on the bulk-invasion sequences produced by drainage. 'queue' walks the invasion in reverse using a priority queue and is faster on ibip/qbip-style step-by-step sequences. The two return the same answer.

trap_labels = ps.filters.find_trapped_clusters(
    im=im, seq=drn.im_seq, outlets=outlets, method='labels')
trap_queue = ps.filters.find_trapped_clusters(
    im=im, seq=drn.im_seq, outlets=outlets, method='queue')

fig, ax = plt.subplots(1, 2, figsize=[10, 5])
ax[0].imshow(trap_labels, origin='lower', interpolation='none')
ax[0].set_title("method = 'labels'")
ax[0].axis(False)
ax[1].imshow(trap_queue, origin='lower', interpolation='none')
ax[1].set_title("method = 'queue'")
ax[1].axis(False);

min_size

Trapped clusters smaller than this many voxels are not flagged. Useful for stripping pixel-scale digital artefacts that pile up against solid walls.

trap0 = ps.filters.find_trapped_clusters(
    im=im, seq=drn.im_seq, outlets=outlets, min_size=0)
trap5 = ps.filters.find_trapped_clusters(
    im=im, seq=drn.im_seq, outlets=outlets, min_size=5)

fig, ax = plt.subplots(1, 2, figsize=[10, 5])
ax[0].imshow(trap0, origin='lower', interpolation='none')
ax[0].set_title('min_size = 0')
ax[0].axis(False)
ax[1].imshow(trap5, origin='lower', interpolation='none')
ax[1].set_title('min_size = 5')
ax[1].axis(False);

conn

Controls voxel connectivity used when grouping trapped voxels. 'min' (default) requires shared faces; 'max' accepts edges and corners.

trap_min = ps.filters.find_trapped_clusters(
    im=im, seq=drn.im_seq, outlets=outlets, conn='min')
trap_max = ps.filters.find_trapped_clusters(
    im=im, seq=drn.im_seq, outlets=outlets, conn='max')

print("conn = 'min':", int(trap_min.sum()), 'voxels')
print("conn = 'max':", int(trap_max.sum()), 'voxels')

conn = 'min': 9072 voxels
conn = 'max': 9068 voxels