基于C# NetTopologySuite从相交线提取目标多边形的技术问题

我需要提取示例中的边界多边形，目前在C#中使用NetTopologySuite（与JTS库功能类似），但无法得到预期的红色目标多边形，求解决方法。

初始实现代码 #

Document doc = Autodesk.AutoCAD.ApplicationServices.Application.DocumentManager.MdiActiveDocument;
Database db = doc.Database;
Editor ed = doc.Editor;

PromptEntityOptions pEntOpt1 = new PromptEntityOptions("Outter Boundary");
pEntOpt1.SetRejectMessage("is Not Polyline");
pEntOpt1.AddAllowedClass(typeof(Polyline), true);
PromptEntityResult pEntRes1 = ed.GetEntity(pEntOpt1);

string typeName = RXObject.GetClass(typeof(Polyline)).DxfName;
TypedValue[] tv = new TypedValue[1] { new TypedValue((int)DxfCode.Start, typeName) };
SelectionFilter sf = new SelectionFilter(tv);
PromptSelectionResult pSelectRes = ed.GetSelection(sf);

if (pSelectRes.Status != PromptStatus.OK)
    return;

ObjectId boudaryPlineId = pEntRes1.ObjectId;
ObjectId[] innerPlineids = pSelectRes.Value.GetObjectIds();
ObjectIdCollection innerBoundaries = new ObjectIdCollection(innerPlineids);

try
{
    using (doc.LockDocument())
    {
        using (Transaction tr = db.TransactionManager.StartTransaction())
        {
            Polygonizer polygonizer = new Polygonizer();
            GeometryFactory gf = new GeometryFactory();
            Polyline boundaryPline = tr.GetObject(boudaryPlineId, OpenMode.ForWrite) as Polyline;
            Coordinate[] coords = new Coordinate[boundaryPline.NumberOfVertices + 1];
            for (int j = 0; j < boundaryPline.NumberOfVertices; j++)
            {
                Point3d pos = boundaryPline.GetPoint3dAt(j);
                coords[j] = new Coordinate(pos.X, pos.Y);
            }
            coords[boundaryPline.NumberOfVertices] = new Coordinate(boundaryPline.StartPoint.X, boundaryPline.StartPoint.Y);
            Polygon pg = gf.CreatePolygon(coords);
            List<Geometry> plines = new List<Geometry>();
            foreach (ObjectId indexid in innerBoundaries)
            {
                Polyline indexPline = tr.GetObject(indexid, OpenMode.ForWrite) as Polyline;
                Coordinate[] coords2 = new Coordinate[indexPline.NumberOfVertices];
                for (int i = 0; i < indexPline.NumberOfVertices; i++)
                {
                    Point3d pos = indexPline.GetPoint3dAt(i);
                    coords2[i] = new Coordinate(pos.X, pos.Y);
                }
                LineString ls1 = new LineString(coords2);
                polygonizer.Add(ls1);
            }
            ICollection<Geometry> test = polygonizer.GetPolygons();
            foreach (Geometry polygon in test)
            {
                // to do 
            }
            tr.Commit();
        }
    }
}
catch
{

}

相关图示 #

应用修改方案后的代码 #

private List<NetGeometry> GetPolygons(Transaction tr, List<LineString> lineStrings)
{
    List<NetGeometry> polygons = new List<NetGeometry>();
    Polygonizer polygonizer = new Polygonizer(false);

    GeometryFactory gf = new GeometryFactory(new PrecisionModel(10000));
    var noder = new SnapRoundingNoder(new PrecisionModel(10000)); // 按需调整PrecisionModel，必须为固定精度
    noder.ComputeNodes(lineStrings.Select(s => (ISegmentString)new NodedSegmentString(s.Coordinates, s)).ToList());
    var noded = noder.GetNodedSubstrings();
    polygonizer.Add(noded.Select(n => (Geometry)gf.CreateLineString(n.Coordinates)).ToList());

    //for ( int i = 0; i < lineStrings.Count; i++)
    //{
    //  polygonizer.Add(lineStrings[i]);
    //}
    ICollection<NetGeometry> result = polygonizer.GetPolygons();

    foreach (NetGeometry index in result)
    {
        if ( index is Polygon pg)
        {
            polygons.Add(pg);
        }
    }
    return polygons;
}

修改后结果图示 #

内容的提问来源于stack exchange，提问作者Hyeseong