使用 Python、Shapely 和 Fiona 编辑多边形坐标

问题描述

我需要编辑相交多边形的几何图形，但我不知道如何将修改后的几何图形保存到 shapefile。甚至有可能吗？

from shapely.geometry import polygon,shape
import matplotlib.pyplot as plt
import fiona


c = fiona.open('polygon23.shp','r')
d = fiona.open('polygon23.shp','r')

for poly in c.values():
    for poly2 in d.values():
        p_poly = shape(poly['geometry'])
        p_poly2 = shape(poly2['geometry'])
        intersect_polygons = p_poly.intersection(p_poly2)
        if type(intersect_polygons) == polygon:
            intersect_polygons = p_poly.intersection(p_poly2).exterior.coords
            if p_poly.exterior.xy != p_poly2.exterior.xy:

                y_difference = abs(intersect_polygons[0][1]) - abs(intersect_polygons[2][1])
                
                coords_polygonB = p_poly2.exterior.coords[:]
                
                coords_polygonB[0] = (coords_polygonB[0][0],coords_polygonB[0][1] + (y_difference))
                coords_polygonB[1] = (coords_polygonB[1][0],coords_polygonB[1][1] + (y_difference))
                coords_polygonB[2] = (coords_polygonB[2][0],coords_polygonB[2][1] + (y_difference))
                coords_polygonB[3] = (coords_polygonB[3][0],coords_polygonB[3][1] + (y_difference))
                coords_polygonB[4] = (coords_polygonB[4][0],coords_polygonB[4][1] + (y_difference))
                
                p_poly2 = polygon(coords_polygonB)

                x,y = p_poly.exterior.xy
                plt.plot(x,y)
                x,y = p_poly2.exterior.xy
                plt.plot(x,y)
                plt.show()

解决方法

去除许多多边形之间的交叉点很可能是一个复杂的问题。此外，我在我的解决方案中使用了您的方法作为求解器。

答案

你的问题的答案是肯定的。您可以在 shp 文件中纠正多边形之间的交叉点；但是，您需要创建新的 Polygon 对象，您不能只更改现有 Polygon 的外部坐标。

从原始 shp 文件中存储元数据和光盘

下面的解决方案将生成的多边形集写入/创建到新的 shp 文件。这需要我们存储原始 shp 文件中的元数据，并将其传递给新文件。我们还需要存储每个多边形的属性，我将它们存储在一个单独的列表中，set_of_properties。

不需要两个 for 循环

您不需要 for 循环，只需使用 itertools 标准库中的组合来循环遍历所有可能的多边形组合。我使用索引组合来替换与新多边形相交的多边形。

外部 do...while 循环

在非常糟糕的情况下，使用您的方法进行纠正实际上可能会引入新的交叉点。我们可以捕获这些并通过循环求解器来纠正它们，直到没有交叉点为止。这需要一个 do...while 循环，但 Python 中没有 do...while 循环。此外，它可以用while循环来实现（参见实现方案）。

解决方案

from itertools import combinations

from shapely.geometry import Polygon,Point,shape,mapping
import matplotlib.pyplot as plt
import fiona

SHOW_NEW_POLYGONS = False

polygons,set_of_properties = [],[]
with fiona.open("polygon23.shp","r") as source:
    for line in source:
        polygons.append(shape(line["geometry"]))
        set_of_properties.append(line["properties"])
    meta = source.meta

poly_index_combinations = combinations(tuple(range(len(polygons))),2)
while True:
    intersection_record = []
    for i_poly_a,i_poly_b in poly_index_combinations:
        poly_a,poly_b = polygons[i_poly_a],polygons[i_poly_b]
        if poly_a.exterior.xy == poly_b.exterior.xy:
            # print(f"The polygons have identical exterior coordinates:\n{poly_a} and {poly_b}\n")
            continue

        intersecting = poly_a.intersection(poly_b)
        if type(intersecting) != Polygon:
            continue
        intersecting_polygons = intersecting.exterior.coords
        if not intersecting_polygons:
            # print(f"No intersections between\n{poly_a} and {poly_b}\n")
            continue

        print("Rectifying intersection")
        y_diff = abs(intersecting_polygons[0][1]) - abs(intersecting_polygons[2][1])

        new_poly_b = Polygon((
            Point(float(poly_b.exterior.coords[0][0]),float(poly_b.exterior.coords[0][1] + y_diff)),Point(float(poly_b.exterior.coords[1][0]),float(poly_b.exterior.coords[1][1] + y_diff)),Point(float(poly_b.exterior.coords[2][0]),float(poly_b.exterior.coords[2][1] + y_diff)),Point(float(poly_b.exterior.coords[3][0]),float(poly_b.exterior.coords[3][1] + y_diff)),Point(float(poly_b.exterior.coords[4][0]),float(poly_b.exterior.coords[4][1] + y_diff))
        ))

        if SHOW_NEW_POLYGONS:
            x,y = poly_a.exterior.xy
            plt.plot(x,y)
            x,y = new_poly_b.exterior.xy
            plt.plot(x,y)
            plt.show()

        polygons[i_poly_b] = new_poly_b
        intersection_record.append(True)

    if not intersection_record:
        break

with fiona.open("new.shp","w",**meta) as sink:
    for poly,properties in zip(polygons,set_of_properties):
        sink.write({
            "geometry": mapping(poly),"properties": properties
        })

fiona matplotlib python shapefile shapely