mirror of
https://github.com/wassname/scikit-image.git
synced 2026-06-27 23:39:49 +08:00
Vighnesh Birodkar
58 lines
1.3 KiB
Python
58 lines
1.3 KiB
Python
"""
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=======================
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Region Adjacency Graphs
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=======================
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This example demonstrates the use of `merge_nodes` function of a Region
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Adjacency Graph (RAG). When a new node is formed by merging two nodes, the edge
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weight of all the edges incident on it can be updated by a user defined
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function `weight_func`.
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The default behaviour is to use the smaller edge weight incase of a conflict.
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The example below also shows how to use a custom function to take the larger
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weight instead.
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"""
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from skimage.graph import rag
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import networkx as nx
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from matplotlib import pyplot as plt
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import numpy as np
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def max_edge(g, src, dst, n):
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w1 = g[n].get(src, {'weight': -np.inf})['weight']
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w2 = g[n].get(dst, {'weight': -np.inf})['weight']
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return max(w1, w2)
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def display(g, title):
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pos = nx.circular_layout(g)
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plt.figure()
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plt.title(title)
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nx.draw(g, pos)
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nx.draw_networkx_edge_labels(g, pos, font_size=20)
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g = rag.RAG()
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g.add_edge(1, 2, weight=10)
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g.add_edge(2, 3, weight=20)
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g.add_edge(3, 4, weight=30)
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g.add_edge(4, 1, weight=40)
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g.add_edge(1, 3, weight=50)
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# Assigning dummy labels.
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for n in g.nodes():
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g.node[n]['labels'] = [n]
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gc = g.copy()
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display(g, "Original Graph")
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g.merge_nodes(1, 3)
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display(g, "Merged with default (min)")
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gc.merge_nodes(1, 3, weight_func=max_edge)
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display(gc, "Merged with max")
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plt.show()
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