Python 射線法判斷一個點坐標是否在一個坐標區域內

class Point:
    lng = ''
    lat = ''

    def __init__(self, lng, lat):
        self.lng = lng
        self.lat = lat


# 求外包矩形
def get_polygon_bounds(points):
    length = len(points)
    top = down = left = right = points[0]
    for i in range(1, length):
        if points[i].lng > top.lng:
            top = points[i]
        elif points[i].lng < down.lng:
            down = points[i]
        else:
            pass
        if points[i].lat > right.lat:
            right = points[i]
        elif points[i].lat < left.lat:
            left = points[i]
        else:
            pass
    top_left = Point(top.lng, left.lat)
    top_right = Point(top.lng, right.lat)
    down_right = Point(down.lng, right.lat)
    down_left = Point(down.lng, left.lat)
    return [top_left, top_right, down_right, down_left]


# 判斷點是否在外包矩形外
def is_point_in_rect(point, polygon_bounds):
    top_left = polygon_bounds[0]
    top_right = polygon_bounds[1]
    down_right = polygon_bounds[2]
    down_left = polygon_bounds[3]
    return (down_left.lng <= point.lng <= top_right.lng
            and top_left.lat <= point.lat <= down_right.lat)


def is_point_in_polygon(point, points):
    polygon_bounds = get_polygon_bounds(points)
    if not is_point_in_rect(point, polygon_bounds):
        return False
    length = len(points)
    point_start = points[0]
    flag = False
    for i in range(1, length):
        point_end = points[i]
        # 點與多邊形頂點重合
        if (point.lng == point_start.lng and point.lat == point_start.lat) or (
                point.lng == point_end.lng and point.lat == point_end.lat):
            return True
        # 判斷線段兩端點是否在射線兩側
        if (point_end.lat < point.lat <= point_start.lat) or (
                point_end.lat >= point.lat > point_start.lat):
            # 線段上與射線 Y 坐標相同的點的 X 坐標
            if point_end.lat == point_start.lat:
                x = (point_start.lng + point_end.lng) / 2
            else:
                x = point_end.lng - (point_end.lat - point.lat) * (
                        point_end.lng - point_start.lng) / (
                        point_end.lat - point_start.lat)
            # 點在多邊形的邊上
            if x == point.lng:
                return True
            # 射線穿過多邊形的邊界
            if x > point.lng:
                flag = not flag
            else:
                pass
        else:
            pass

        point_start = point_end
    return flag


def test(input_lng=116.732617, input_lat=39.722676):
    # polyline 是多個坐標點，形如
    # ['116.732617,39.722676', '116.732617,39.722676', '116.732617,39.722676',
    # '116.732617,39.722676', '116.732617,39.722676']
    polyline = []

    points = []
    for line in polyline:
        if line:
            try:
                lng, lat = line.split(',')
                points.append(Point(float(lng), float(lat)))
            except ValueError:
                pass
    if points:
        is_point_in_polygon(Point(float(input_lng), float(input_lat)), points)

　　缺點：慢

 

替代方法，類似的坐標的需求可以集成 https://geoalchemy-2.readthedocs.io/en/latest/