def naxes_connectivity(I):
# Get the pixels we want to check (exclude edge pixels)
Ir = np.ravel(I)
edgeidcs = iu.edge_coords(I.shape, dtype='flat')
allpix = set(np.where(Ir == 1)[0])
dopix = allpix - edgeidcs
savepix = list(dopix)
naxes = []
while dopix:
pix = dopix.pop()
count = 0
if Ir[pix + 1] == 1 or Ir[pix - 1] == 1:
count = count + 1
if Ir[pix + I.shape[1]] == 1 or Ir[pix - I.shape[1]] == 1:
count = count + 1
if Ir[pix + 1 + I.shape[1]] == 1 or Ir[pix - 1 - I.shape[1]] == 1:
count = count + 1
if Ir[pix - 1 + I.shape[1]] == 1 or Ir[pix + 1 - I.shape[1]] == 1:
count = count + 1
naxes.append(count)
Inax = np.zeros_like(Ir, dtype=np.uint8)
Inax[savepix] = naxes
Inax = np.reshape(Inax, I.shape)
return Inax
def test_edge_coords():
"""Test edge_coords() function."""
I = np.zeros((3, 3))
sizeI = np.shape(I)
edgepts = im_utils.edge_coords(sizeI, dtype='xy')
# make assertions to known edge coordinates in x and y
assert np.all(edgepts[0] == [0, 0, 0, 0, 1, 2, 2, 2, 2, 2, 1, 0])
assert np.all(edgepts[1] == [0, 1, 2, 2, 2, 2, 2, 1, 0, 0, 0, 0])
def isbp_walk_for_bps(I, bpi):
bpi = set(bpi)
# Use raveled image
Ir = np.ravel(I)
# Get edge pixels
edgeidcs = iu.edge_coords(I.shape, dtype='flat')
# Get emanators from first bp
do_first = set() # These are the 4-connected emanators
emanators = set()
for bp in bpi:
emanators = emanators | set(iu.neighbors_flat(bp, Ir, I.shape[1])[0])
do_first.update(iu.four_conn([bp], I)[0])
# Create set containing pixels that have already been visited
walked = bpi | emanators
while emanators:
if do_first:
idx = do_first.pop()
emanators.remove(idx)
else:
idx = emanators.pop()
walking = 1
while walking:
walked.add(idx)
neighs = set(iu.neighbors_flat(idx, Ir, I.shape[1])[0])
neighs = neighs - walked
if len(neighs) == 0:
walking = 0
elif len(neighs) == 1:
idx = neighs.pop()
if idx in edgeidcs:
walking = 0
else:
bpi.add(idx)
fourconn = iu.four_conn([idx], I)[0]
fourconn = [f for f in fourconn if f in neighs]
do_first.update(fourconn)
emanators = emanators | neighs
walked.add(idx)
walked.update(neighs)
return bpi
def naxes_connectivity(I):
"""
Compute number of axes of connectivity.
Computes the number of axes of connectivity for each pixel in an input
skeleton. The maximum is four; horizontal, vertical, and two diagonals.
The number of axes of pixel connectivity is used to determine where to
place branchpoints.
Parameters
----------
I : np.ndarray
Binary image of a skeleton. In RivGraph, the skeleton is a reduced and
padded version of Iskel.
Returns
-------
Inax : np.ndarray
Same shape as I; values correspond to the number of axes represented
by each pixel's connectivity.
"""
# Get the pixels we want to check (exclude edge pixels)
Ir = np.ravel(I)
edgeidcs = iu.edge_coords(I.shape, dtype='flat')
allpix = set(np.where(Ir == 1)[0])
dopix = allpix - edgeidcs
savepix = list(dopix)
naxes = []
while dopix:
pix = dopix.pop()
count = 0
if Ir[pix + 1] == 1 or Ir[pix - 1] == 1:
count = count + 1
if Ir[pix + I.shape[1]] == 1 or Ir[pix - I.shape[1]] == 1:
count = count + 1
if Ir[pix + 1 + I.shape[1]] == 1 or Ir[pix - 1 - I.shape[1]] == 1:
count = count + 1
if Ir[pix - 1 + I.shape[1]] == 1 or Ir[pix + 1 - I.shape[1]] == 1:
count = count + 1
naxes.append(count)
Inax = np.zeros_like(Ir, dtype=np.uint8)
Inax[savepix] = naxes
Inax = np.reshape(Inax, I.shape)
return Inax
def isbp_walk_for_bps(I, bpi):
"""
Find branchpoints by walking from a pixel.
Finds branchpoints by ensuring that all pixels in the sub-skeleton can be
walked to from the set of already-found branchpoints, without visiting
the same pixel more than once.
Parameters
----------
I : np.ndarray
Binary image of a skeleton. In RivGraph, the skeleton is a reduced and
padded version of Iskel.
bpi : list
Indices within I of the branchpoint to begin walk.
Returns
-------
bpi : list
Branchpoint indices in I.
"""
bpi = set(bpi)
# Use raveled image
Ir = np.ravel(I)
# Get edge pixels
edgeidcs = iu.edge_coords(I.shape, dtype='flat')
# Get emanators from first bp
do_first = set() # These are the 4-connected emanators
emanators = set()
for bp in bpi:
emanators = emanators | set(iu.neighbors_flat(bp, Ir, I.shape[1])[0])
do_first.update(iu.four_conn([bp], I)[0])
# Create set containing pixels that have already been visited
walked = bpi | emanators
while emanators:
if do_first:
idx = do_first.pop()
emanators.remove(idx)
else:
idx = emanators.pop()
walking = 1
while walking:
walked.add(idx)
neighs = set(iu.neighbors_flat(idx, Ir, I.shape[1])[0])
neighs = neighs - walked
if len(neighs) == 0:
walking = 0
elif len(neighs) == 1:
idx = neighs.pop()
if idx in edgeidcs:
walking = 0
else:
bpi.add(idx)
fourconn = iu.four_conn([idx], I)[0]
fourconn = [f for f in fourconn if f in neighs]
do_first.update(fourconn)
emanators = emanators | neighs
walked.add(idx)
walked.update(neighs)
return bpi
def isbp_parsimonious(Ic, Icr, Inar, Infr):
"""
Computes parsimonious set of branchpoints.
Parameters
----------
Ic : np.ndarray
Image of possible branchpoints; values correspond to number of
neighbors.
Icr : np.ndarray
Raveled (np.ravel) version of Ic.
Inar : np.ndarray
Raveled version of image returned by naxes_connectivity.
Infr : np.ndarray
Raveled version of image returned by nfour_connectivity.
Returns
-------
bps : list
All branchpoint indices within Ic.
"""
# Find all possible branchpoints by considerng those with conn>2
bp_poss = np.where(Ic > 2)
bp_poss_i = np.ravel_multi_index(bp_poss, Ic.shape)
bp_poss_i = list(set(bp_poss_i) - iu.edge_coords(Ic.shape))
# Find all possible branchpoint combinations by walking from each
# possible initial branchpoint
bpsave = []
for bpi in bp_poss_i:
bptemp = isbp_walk_for_bps(np.array(Ic, dtype=np.bool), [bpi])
bpsave.append(bptemp)
# Number of branchpoints for each possible initial branchpoint
bpcounts = [len(b) for b in bpsave]
bpsolo = [bpsave[i].pop() for i, c in enumerate(bpcounts) if c == 1]
# If only one branchpoint is required, use it. However, there could be
# multiple branchpoints that can serve as the single; use the one with
# highest naxes-connectivity; if there are still multiple choices, take the
# highest 4-connectivity. If there are still no unique choices, choose the
# highest 4-connected among the highest naxes-connected.
if len(bpsolo) > 0:
naxconn = Inar[bpsolo]
maxnax = [
bps for bps, nl in zip(bpsolo, naxconn) if nl == max(naxconn)
]
if len(maxnax) == 1:
return [maxnax]
else:
fourconn = Infr[bpsolo]
maxfour = [
bpsolo[i] for i, fc in enumerate(fourconn)
if fc == max(fourconn)
]
if len(maxfour) == 1:
return [maxfour]
# Now see if there's a max 4-conn within the max naxes-conn
fourconn = Infr[maxnax]
maxfour = [
maxnax[i] for i, fc in enumerate(fourconn) if fc == max(fourconn)
]
return [min(maxfour)]
# Set bp_must according to conn, naxes, nfour
keepvals = [[6, 4, 2], [5, 3, 1], [5, 3, 4], [3, 3, 2], [3, 3, 1],
[4, 2, 4]]
bp_must = []
for kv in keepvals:
keeps = np.ndarray.tolist(
np.where(
np.logical_and(np.logical_and(Icr == kv[0], Inar == kv[1]),
Infr == kv[2]) == 1)[0])
bp_must = bp_must + keeps
# Special cases - 4,4,2 - choose one
keepvals = [[4, 4, 2]]
for kv in keepvals:
keeps = np.ndarray.tolist(
np.where(
np.logical_and(np.logical_and(Icr == kv[0], Inar == kv[1]),
Infr == kv[2]) == 1)[0])
if len(keeps) == 2:
bp_must = bp_must + [keeps[0]]
# Only consider combinations that have branchpoints where they must be placed
if len(bp_must) > 0:
bps = isbp_walk_for_bps(np.array(Ic, dtype=np.bool), bp_must)
return bps
# If there are no branchpoints that must exist based on patterns,
# use the set with the smallest number of branchpoints. If there are multiple
# sets, we move on...
mincount = min(bpcounts)
minidcs = [i for i, bpi in enumerate(bpcounts) if bpi == mincount]
if len(minidcs) == 1:
return bpsave[minidcs[0]]
# Finally, choose branchpoints based on the most common branchpoints created
# when walking from all possible branchpoints
mode = stats.mode([p for b in bpsave for p in b])
bp_init = np.ndarray.tolist(mode.mode)
bps = isbp_walk_for_bps(np.array(Ic, dtype=np.bool), bp_init)
return bps
