判断点是否在多边形内

Question

我试图检测给定的点（x，y）是否在 n*2 数组的多边形中。但似乎多边形边界上的某些点返回它不包括在内。

def point_inside_polygon(x,y,poly):

    n = len(poly)
    inside =False

    p1x,p1y = poly[0]
    for i in range(n+1):
        p2x,p2y = poly[i % n]
        if y > min(p1y,p2y):
            if y <= max(p1y,p2y):
                if x <= max(p1x,p2x):
                    if p1y != p2y:
                        xinters = (y-p1y)*(p2x-p1x)/float((p2y-p1y))+p1x
                    if p1x == p2x or x <= xinters:
                        inside = not inside
        p1x,p1y = p2x,p2y

    return inside

Answer 1

这是一个有多个选项的简单方法

from shapely.geometry import Point, Polygon

# Point objects(Geo-coordinates)
p1 = Point(24.952242, 60.1696017)
p2 = Point(24.976567, 60.1612500)

# Polygon
coords = [(24.950899, 60.169158), (24.953492, 60.169158), (24.953510, 60.170104), (24.950958, 60.169990)]
poly = Polygon(coords)

方法一：

在函数内使用：

语法：point.within(polygon)

# Check if p1 is within the polygon using the within function
print(p1.within(poly))
# True

# Check if p2 is within the polygon
print(p2.within(poly))
# False

方法二：

使用 contains 函数：

语法：polygon.contains(point)

# Check if polygon contains p1 
print(poly.contains(p1))
# True

# Check if polygon contains p2
print(poly.contains(p2))
# False

要检查点是否位于多边形的边界上：

使用触摸功能：

语法：polygon.touches(point)

poly1 = Polygon([(0, 0), (1, 0), (1, 1)])
point1 = Point(0, 0)

poly1.touches(point1)
# True

如果你想加快这个过程，那么请使用

import shapely.speedups
shapely.speedups.enable()

和

使用 Geopandas

参考：

1. https://automating-gis-processes.github.io/CSC18/lessons/L4/point-in-polygon.html#point-in-polygon-using-geopandas

2. https://shapely.readthedocs.io/en/latest/manual.html

3. https://streamhacker.com/2010/03/23/python-point-in-polygon-shapely/