ArcEngine中多边形内外环的处理（转）

ArcEngine中多边形内外环的处理

原创 2012年09月06日 22:49:11

• 标签：
• object /
• null /
• 数据库

• 3462

Polylgon对象是由一个或多个Ring对象的有序集合，它可以是由单个Ring对象构成，也可以使用多个Ring组成如下图所示。其中Ring可以分为Outer Ring(外环)和Inner　Ring(内环)之分。外环和内环都是有方向的，它们的区别是外环的方向是顺时针的，内环的方向是逆时针。如果多边形只有外环，没有内环，很好处理，难得是如何将内环和外环区分开来，并且保证正确的内外环包含关系。

前段时间做MDB数据库的坐标转换功能，由于针对的是地方坐标系，所以无法用7参数构建投影坐标统一转换。我采用的是将featureLayer中的Feature一个一个取出来，将每个点的起始点坐标取出来进行转换，然后再组合回去。现在将多边形部分代码贴出来：

IPolygon4 polygon = pFeature.ShapeCopy as IPolygon4;  
                        IGeometryBag bag = polygon.ExteriorRingBag;     //获取多边形的所有外环
                        IEnumGeometry geo = bag as IEnumGeometry;
                        geo.Reset();
                        IRing exRing = geo.Next() as IRing;
                        while (exRing != null)
                        {
                            IGeometryBag bags = polygon.get_InteriorRingBag(exRing);   //获取当前外环所包含的内环
                            IEnumGeometry geos = bags as IEnumGeometry;
                            geos.Reset();
                            IRing inRing = geos.Next() as IRing;
                            while (inRing != null)   //先处理内环
                            {
                                ISegmentCollection segs = inRing as ISegmentCollection;
                                ISegmentCollection ring = new RingClass();   //创建新的ring对象，以重新组合polygon
                                for (int i = 0; i < segs.SegmentCount; i++)
                                {
                                    object o = Type.Missing;
                                    ISegment s = segs.get_Segment(i);
                                    IPoint fromPoint = s.FromPoint;
                                    IPoint toPoint = s.ToPoint;

x = fromPoint.X;
                                    y = fromPoint.Y;
                                    fromPoint.PutCoords(ConvertTo2000X(x, y), ConvertTo2000Y(x, y));  //将X、Y坐标转换
                                    s.FromPoint = fromPoint;

x1 = toPoint.X;
                                    y1 = toPoint.Y;
                                    toPoint.PutCoords(ConvertTo2000X(x1, y1), ConvertTo2000Y(x1, y1));
                                    s.ToPoint = toPoint;
                                    ring.AddSegment(s, ref o, ref o);
                                }
                                IRing ir = ring as IRing;
                                ir.Close();
                                ppolygon.AddGeometry(ir);
                                inRing = geos.Next() as IRing;
                            }
                            ISegmentCollection seg = exRing as ISegmentCollection;
                            ISegmentCollection rings = new RingClass();
                            for (int i = 0; i < seg.SegmentCount; i++)  //处理外环
                            {
                                object o = Type.Missing;
                                ISegment s = seg.get_Segment(i);
                                IPoint fromPoint = s.FromPoint;
                                IPoint toPoint = s.ToPoint;

x = fromPoint.X;
                                y = fromPoint.Y;
                                fromPoint.PutCoords(ConvertTo2000X(x, y), ConvertTo2000Y(x, y));
                                s.FromPoint = fromPoint;

x1 = toPoint.X;
                                y1 = toPoint.Y;
                                toPoint.PutCoords(ConvertTo2000X(x1, y1), ConvertTo2000Y(x1, y1));
                                s.ToPoint = toPoint;
                                rings.AddSegment(s, ref o, ref o);
                            }
                            IRing irr = rings as IRing;
                            irr.Close();
                            ppolygon.AddGeometry(irr);
                            exRing = geo.Next() as IRing;                           
                        }
                        IPolygon p = ppolygon as IPolygon;
                        p.SimplifyPreserveFromTo();    //保证多边形封闭
                        pFeature.Shape = p;  
                        pFeature.Store();

通过以上的方法能够将polygon取出来，实现自定义的坐标转换过程，由于先取出来然后再重新组合，所以效率不是很高，但是经过大数据量的验证，表明效率能够接受。