Welcome to OGeek Q&A Community for programmer and developer-Open, Learning and Share
Welcome To Ask or Share your Answers For Others

Categories

0 votes
449 views
in Technique[技术] by (71.8m points)

python - Find coordinate of the closest point on polygon in Shapely

Say I have the following Polygon and Point:

>>> poly = Polygon([(0, 0), (2, 8), (14, 10), (6, 1)])
>>> point = Point(12, 4)

enter image description here

I can calculate the point's distance to the polygon...

>>> dist = point.distance(poly)
>>> print(dist)
2.49136439561

...but I would like to know the coordinate of the point on the polygon border where that shortest distance measures to.

My initial approach is to buffer the point by its distance to the polygon, and find the point at which that circle is tangent to the polygon:

>>> buff = point.buffer(dist) 

enter image description here However, I'm not sure how to calculate that point. The two polygon's don't intersect so list(poly.intersection(buff)) will not give me that point.

Am I on the right track with this? Is there a more straightforward method?

See Question&Answers more detail:os

与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
Welcome To Ask or Share your Answers For Others

1 Reply

0 votes
by (71.8m points)

While the answer of eguaio does the job, there is a more natural way to get the closest point using shapely.ops.nearest_points function:

from shapely.geometry import Point, Polygon
from shapely.ops import nearest_points

poly = Polygon([(0, 0), (2, 8), (14, 10), (6, 1)])
point = Point(12, 4)
# The points are returned in the same order as the input geometries:
p1, p2 = nearest_points(poly, point)
print(p1.wkt)
# POINT (10.13793103448276 5.655172413793103)

The result is the same as in the other answer:

from shapely.geometry import LinearRing
pol_ext = LinearRing(poly.exterior.coords)
d = pol_ext.project(point)
p = pol_ext.interpolate(d)
print(p.wkt)
# POINT (10.13793103448276 5.655172413793103)
print(p.equals(p1))
# True

与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
OGeek|极客中国-欢迎来到极客的世界,一个免费开放的程序员编程交流平台!开放,进步,分享!让技术改变生活,让极客改变未来! Welcome to OGeek Q&A Community for programmer and developer-Open, Learning and Share
Click Here to Ask a Question

...