mirror of
https://github.com/wassname/scikit-image.git
synced 2026-07-17 11:32:45 +08:00
Juan Nunez-Iglesias
dc377970f5
The join of two segmentations is the segmentation in which two voxels are in the same segment if and only if they are in the same segment in both input segmentations.
94 lines
3.0 KiB
Python
94 lines
3.0 KiB
Python
import numpy as np
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def join_segmentations(s1, s2):
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"""Return the join of the two input segmentations.
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The join J of S1 and S2 is defined as the segmentation in which two voxels
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are in the same segment in J if and only if they are in the same segment
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in *both* S1 and S2.
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Parameters
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----------
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s1, s2 : numpy arrays
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s1 and s2 are label fields of the same shape.
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Returns
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-------
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j : numpy array
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The join segmentation of s1 and s2.
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Examples
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--------
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>>> import numpy as np
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>>> from skimage.segmentation import join_segmentations
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>>> s1 = np.array([[0, 0, 1, 1],
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... [0, 2, 1, 1],
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... [2, 2, 2, 1]])
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>>> s2 = np.array([[0, 1, 1, 0],
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... [0, 1, 1, 0],
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... [0, 1, 1, 1]])
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>>> join_segmentations(s1, s2)
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array([[0, 1, 3, 2],
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[0, 5, 3, 2],
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[4, 5, 5, 3]])
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"""
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if s1.shape != s2.shape:
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raise ValueError("Cannot join segmentations of different shape. " +
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"s1.shape: %s, s2.shape: %s" % (s1.shape, s2.shape))
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s1 = relabel_from_one(s1)[0]
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s2 = relabel_from_one(s2)[0]
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j = (s2.max() + 1) * s1 + s2
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j = relabel_from_one(j)[0]
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return j
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def relabel_from_one(ar):
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"""Convert array ar of arbitrary labels to labels 1...len(np.unique(ar))+1
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This function also returns the forward map (mapping the original labels to
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the reduced labels) and the inverse map (mapping the reduced labels back
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to the original ones).
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Parameters
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----------
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ar : numpy ndarray (integer type)
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Returns
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-------
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ar_relabeled : numpy array of same shape as ar
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forward_map : 1d numpy array of length np.unique(ar) + 1
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inverse_map : 1d numpy array of length len(np.unique(ar))
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The length is len(np.unique(ar)) + 1 if 0 is not in np.unique(ar)
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Examples
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--------
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>>> import numpy as np
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>>> from skimage.segmentation import relabel_from_one
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>>> ar = array([1, 1, 5, 5, 8, 99, 42])
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>>> ar_relab, fw, inv = relabel_from_one(ar)
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>>> ar_relab
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array([1, 1, 2, 2, 3, 5, 4])
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>>> fw
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array([0, 1, 0, 0, 0, 2, 0, 0, 3, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 4, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 5])
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>>> inv
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array([ 0, 1, 5, 8, 42, 99])
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>>> (fw[ar] == ar_relab).all()
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True
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>>> (inv[ar_relab] == ar).all()
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True
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"""
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labels = np.unique(ar)
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labels0 = labels[labels != 0]
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m = labels.max()
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if m == len(labels0): # nothing to do, already 1...n labels
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return ar, labels, labels
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forward_map = np.zeros(m+1, int)
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forward_map[labels0] = np.arange(1, len(labels0) + 1)
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if not (labels == 0).any():
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labels = np.concatenate(([0], labels))
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inverse_map = labels
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return forward_map[ar], forward_map, inverse_map
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