【NetTopologySuite库】使用Polygonizer线构面，并获取割边、悬挂边、无效环

效果图

进行线构面：

• 构成了两个多边形ABCD、EFGH
• DI、IE是割边（CutEdge）
• 有三条悬挂边：CK、FJ、OP
• 有自相交的无效环：ALMN

示例代码

            var r = new WKTReader();

            var wkts = new string[]
            {
                "linestring(0 0,3 0)",
                "linestring(3 3,3 0)",
                "linestring(3 3,0 3)",
                "linestring(0 0,0 3)",
                "linestring(4 2,0 3)",
                "linestring(0 3,-1 4)",
                "linestring(0 5,-1 4)",
                "linestring(0 5,2 5)",
                "linestring(2 7,2 5)",
                "linestring(2 7,0 7)",
                "linestring(0 5,0 7)",
                "linestring(2 5,4 6)",
                "linestring(-3 3,-3 5)",
                "linestring(0 0,-3 2)",
                "linestring(-1 2,-3 2)",
                "linestring(-1 2,-3 0)",
                "linestring(0 0,-3 0)",
            };
            var lines = wkts.Select(x => r.Read(x)).ToList();
            var pz = new Polygonizer();
            foreach (var line in lines)
            {
                pz.Add(line);
            }
            var dangles = pz.GetDangles();
            var cutEdges = pz.GetCutEdges();
            var invalidRings = pz.GetInvalidRingLines();
            var polygons = pz.GetPolygons();

            Console.WriteLine("多边形：");
            foreach (var polygon in polygons)
            {
                Console.WriteLine(polygon.AsText());
            }
            Console.WriteLine("\n悬挂边：");
            foreach (var item in dangles)
            {
                Console.WriteLine(item.AsText());
            }
            Console.WriteLine("\n割边：");
            foreach (var item in cutEdges)
            {
                Console.WriteLine(item.AsText());
            }
            Console.WriteLine("\n无效环：");
            foreach (var item in invalidRings)
            {
                Console.WriteLine(item.AsText());
            }

打印结果：

多边形：
POLYGON ((3 0, 0 0, 0 3, 3 3, 3 0))
POLYGON ((2 5, 0 5, 0 7, 2 7, 2 5))

悬挂边：
LINESTRING (2 5, 4 6)
LINESTRING (4 2, 0 3)
LINESTRING (-3 3, -3 5)

割边：
LINESTRING (0 3, -1 4)
LINESTRING (0 5, -1 4)

无效环：
LINESTRING (0 0, -3 2, -1 2, -3 0, 0 0)
LINESTRING (-3 2, 0 0, -3 0, -1 2, -3 2)