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随着百度、谷歌等在线地图中出现点聚合显示,即用少量的点或图标来表示地图中的所有点,让地图显示更清晰明朗。有人会问了,SuperMap iObjects .NET可以实现这一可视化吗?回答当然是可以的,下面就跟着我一步一步的来看看具体是如何实现的吧。
一:前期准备: 数据准备:首先需要准备需要聚合的点数据,以及地图底图: 确定聚合算法:本聚合显示采用的是基于网格算法。 二:实现步骤 1、为了方便存放在程序过程中生成的一些显示数据,所以新建了一个内存数据源"mdata"来存放数据;DatasourceConnectionInfo datasourceConnnectionInfo = new DatasourceConnectionInfo();datasourceConnnectionInfo.EngineType = EngineType.UDB;datasourceConnnectionInfo.Server = ":memory:"datasourceConnnectionInfo.Alias = "mdata";
2、由于本次使用的是基于网格的算法,所以首先要根据地图窗口的可视范围新建一个地图网格数据,将生成的网格数据添加到新建的数据源中"mapgrid";
生成代码如下:
DatasetVector datasetvectorgrid = workspace.Datasources["mdata"].Datasets["mapgrid"] as DatasetVector; Recordset recordset = datasetvectorgrid.GetRecordset(false, CursorType.Dynamic); Rectangle2D maprectangle = new Rectangle2D(); maprectangle = mapcontrol.Map.ViewBounds; double distancex = (maprectangle.Right - maprectangle.Left) / 10; double distancey = (maprectangle.Top - maprectangle.Bottom) / 9; Point2D point2d = new Point2D(); rectangles = new Rectangle2D[100]; Array .Clear (rectangles ,0, rectangles .Length ); int count = 0; For (int j = 0; j <= 8; j++) { for (int i = 0; i <= 9; i++) { point2d.X = maprectangle.Left + distancex * i; point2d.Y = maprectangle.Bottom + distancey * j; Rectangle2D rectangle = new Rectangle2D(point2d, distancex, distancey); rectangles[count] = rectangle; count++; GeoRectangle georectangle = new GeoRectangle(rectangle, 0); GeoStyle style = Setgeostyle(); georectangle.Style = style; recordset.AddNew(georectangle); recordset.Update(); } }
3、计算每一个网格里面有多少个点,并且将将聚合点聚合在当前网格内点对象的中心,将聚合点对象添加到内存数据源“point”,将聚合点数以字段的方式存储,对于在网格线上的点则做优先选择处理,
实现代码如下://检查是否包含; private void IsCanContain() { //聚合点数据集; DatasetVector datasetvectorgrid = workspace.Datasources["mdata"].Datasets["point"] as DatasetVector; Recordset recordsetpoint = datasetvectorgrid.GetRecordset(false, CursorType.Dynamic); //原始点数据集; DatasetVector datasetvectorpoint = workspace.Datasources[0].Datasets["POIP"] as DatasetVector; Recordset recordset = datasetvectorpoint.GetRecordset(false, CursorType.Static); //临时单个聚合对象点 DatasetVector datasetvetortpoint = workspace .Datasources ["mdata"].Datasets ["tpoint"] as DatasetVector ; recordsetpoint.DeleteAll(); Point2D[] point2ds = new Point2D[recordset.RecordCount]; int pointitem = 0; for (int i = 0; i < 100; i++) { int count = 0; Rectangle2D rectangle = rectangles[i]; recordset.MoveFirst(); Recordset rectangleitemrecordset = datasetvetortpoint.GetRecordset(false, CursorType.Dynamic); for (int j = 0; j < recordset.RecordCount; j++) { Geometry geometry = recordset.GetGeometry(); GeoPoint geopoint = geometry as GeoPoint ; Point2D point2d = new Point2D (geopoint .X ,geopoint .Y ); if (rectangle .Contains (point2d )) { if (Array.IndexOf(point2ds, point2d) == -1) { count++; point2ds[pointitem] = point2d; pointitem++; GeoPoint itemgeopoint = new GeoPoint(point2d); rectangleitemrecordset.AddNew(itemgeopoint); rectangleitemrecordset.Update(); } } recordset.MoveNext(); }
4、聚合完成后则进行显示聚合点,对上一步骤中生成的聚合点数据集point做分段专题图,进行2—20;20—50;50+进行分段显示不同图标的聚合点,并且将每个聚合点的聚合点数添加到跟中图层进行显示,效果如下:
5、实现选中聚合点的时候将地图中聚合点所表示的分散点显示出来,并且聚合点和聚合点处标签隐藏。实现思路如下:获取选中聚合点处的网格,通过循环判断当前聚合点的分散点有哪些,将分散点的ID存储在数组中,通过图层的过滤显示将分散点显示出来,通过以上步骤,我们的聚合显示就完成啦,效果图如下: