修复 Shapely 中的无效多边形

2022-01-14 00:00:00 python geometry shapely

问题描述

Shapely 将多边形定义为无效，如果它的任何线段相交，包括共线的线段.许多软件包会创建一个带有切口"的区域或区域，如下所示，它具有共线段:

Shapely defines a Polygon as invalid if any of its segments intersect, including segments that are colinear. Many software packages will create a region or area with a "cutout" as shown here which has colinear segments:

>>> pp = Polygon([(0,0), (0,3), (3,3), (3,0), (2,0), 
                  (2,2), (1,2), (1,1), (2,1), (2,0), (0,0)])
>>> pp.is_valid
WARNING:shapely.geos:Self-intersection at or near point 2 0
False

当然，切口可以在 Shapely 中本地实现，或者同样的几何图形可以实现为两个有效的多边形，但如果我只有上面显示的点列表，是否有一个容易修复"的方法(创建有效的此点列表中的几何图形)?

Naturally, the cutout can be implemented natively in Shapely, or this same geometry can be implemented as two valid polygons, but if I only have the list of points shown above, is there an easy to "fix" this (create valid geometry from this list of points)?

解决方案

我找到了适用于特定情况的解决方案:

I found a solution that works for the specific case given:

>>> pp2 = pp.buffer(0)
>>> pp2.is_valid
True
>>> pp2.exterior.coords[:]
[(0.0, 0.0), (0.0, 3.0), (3.0, 3.0), (3.0, 0.0), (2.0, 0.0), (0.0, 0.0)]
>>> pp2.interiors[0].coords[:]
[(2.0, 1.0), (2.0, 2.0), (1.0, 2.0), (1.0, 1.0), (2.0, 1.0)]

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