/usr/lib/python2.7/dist-packages/shapely/examples/intersect.py is in python-shapely 1.6.4-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 | # intersect.py
#
# Demonstrate how Shapely can be used to analyze and plot the intersection of
# a trajectory and regions in space.
from functools import partial
import random
import pylab
from shapely.geometry import LineString, Point
from shapely.ops import cascaded_union
# Build patches as in dissolved.py
r = partial(random.uniform, -20.0, 20.0)
points = [Point(r(), r()) for i in range(100)]
spots = [p.buffer(2.5) for p in points]
patches = cascaded_union(spots)
# Represent the following geolocation parameters
#
# initial position: -25, -25
# heading: 45.0
# speed: 50*sqrt(2)
#
# as a line
vector = LineString(((-25.0, -25.0), (25.0, 25.0)))
# Find intercepted and missed patches. List the former so we can count them
# later
intercepts = [patch for patch in patches.geoms if vector.intersects(patch)]
misses = (patch for patch in patches.geoms if not vector.intersects(patch))
# Plot the intersection
intersection = vector.intersection(patches)
assert intersection.geom_type in ['MultiLineString']
if __name__ == "__main__":
# Illustrate the results using matplotlib's pylab interface
pylab.figure(num=None, figsize=(4, 4), dpi=180)
# Plot the misses
for spot in misses:
x, y = spot.exterior.xy
pylab.fill(x, y, color='#cccccc', aa=True)
pylab.plot(x, y, color='#999999', aa=True, lw=1.0)
# Do the same for the holes of the patch
for hole in spot.interiors:
x, y = hole.xy
pylab.fill(x, y, color='#ffffff', aa=True)
pylab.plot(x, y, color='#999999', aa=True, lw=1.0)
# Plot the intercepts
for spot in intercepts:
x, y = spot.exterior.xy
pylab.fill(x, y, color='red', alpha=0.25, aa=True)
pylab.plot(x, y, color='red', alpha=0.5, aa=True, lw=1.0)
# Do the same for the holes of the patch
for hole in spot.interiors:
x, y = hole.xy
pylab.fill(x, y, color='#ffffff', aa=True)
pylab.plot(x, y, color='red', alpha=0.5, aa=True, lw=1.0)
# Draw the projected trajectory
pylab.arrow(-25, -25, 50, 50, color='#999999', aa=True,
head_width=1.0, head_length=1.0)
for segment in intersection.geoms:
x, y = segment.xy
pylab.plot(x, y, color='red', aa=True, lw=1.5)
# Write the number of patches and the total patch area to the figure
pylab.text(-28, 25,
"Patches: %d/%d (%d), total length: %.1f" \
% (len(intercepts), len(patches.geoms),
len(intersection.geoms), intersection.length))
pylab.savefig('intersect.png')
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