54 lines
1.7 KiB
Python
54 lines
1.7 KiB
Python
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# dissolve.py
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#
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# Demonstrate how Shapely can be used to build up a collection of patches by
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# dissolving circular regions and how Shapely supports plotting of the results.
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from functools import partial
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import random
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import pylab
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from shapely.geometry import Point
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from shapely.ops import unary_union
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# Use a partial function to make 100 points uniformly distributed in a 40x40
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# box centered on 0,0.
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r = partial(random.uniform, -20.0, 20.0)
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points = [Point(r(), r()) for i in range(100)]
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# Buffer the points, producing 100 polygon spots
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spots = [p.buffer(2.5) for p in points]
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# Perform a unary union of the polygon spots, dissolving them into a
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# collection of polygon patches
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patches = unary_union(spots)
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if __name__ == "__main__":
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# Illustrate the results using matplotlib's pylab interface
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pylab.figure(num=None, figsize=(4, 4), dpi=180)
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for patch in patches.geoms:
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assert patch.geom_type in ['Polygon']
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assert patch.is_valid
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# Fill and outline each patch
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x, y = patch.exterior.xy
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pylab.fill(x, y, color='#cccccc', aa=True)
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pylab.plot(x, y, color='#666666', aa=True, lw=1.0)
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# Do the same for the holes of the patch
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for hole in patch.interiors:
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x, y = hole.xy
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pylab.fill(x, y, color='#ffffff', aa=True)
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pylab.plot(x, y, color='#999999', aa=True, lw=1.0)
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# Plot the original points
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pylab.plot([p.x for p in points], [p.y for p in points], 'b,', alpha=0.75)
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# Write the number of patches and the total patch area to the figure
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pylab.text(-25, 25,
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"Patches: %d, total area: %.2f" % (len(patches.geoms), patches.area))
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pylab.savefig('dissolve.png')
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