[转]c# 栅格运算 获得一副DEM地图某个高度以下的范围，并显示

 

private void  GetRasterValue()
{
    IRaster pRaster = pRasLyr.Raster;  //获取已知栅格图层pRasLyr的栅格对象
    IGeoDataset tempGeodata = pRaster as IGeoDataset;
    IMapAlgebraOp rsalgebra = new RasterMapAlgebraOpClass();
    //设置栅格运算空间
    IRasterAnalysisEnvironment rasAnaEnv = (IRasterAnalysisEnvironment)rsalgebra;
    IWorkspaceFactory wsf = new RasterWorkspaceFactoryClass();
    IWorkspace ws = wsf.OpenFromFile("F:\\beifen\\jg", 0);
    rasAnaEnv.OutWorkspace = ws;
    rsalgebra.BindRaster(tempGeodata, "tempRaster");
    //进行栅格运算，height 为已知的整型数据，用来确定高度
    string Opstr = "[tempRaster] < " + height.ToString();
    IGeoDataset outGeoDataset = rsalgebra.Execute(Opstr);
 
    IRasterLayer pCreatRslyr = new RasterLayerClass();
    pCreatRslyr.CreateFromRaster((IRaster)outGeoDataset);
    RasterRender(ref pCreatRslyr);   //对生成的栅格图层进行渲染，是满足要求的按一个颜色显示，不满足要求的栅格不显示
    m_map.AddLayer(pCreatRslyr);
}
//
//栅格图的渲染
//
public void RasterRender(ref IRasterLayer pRasterLayer)
{
    int NumOfClass = 2;
    IRaster pRaster;
    pRaster = pRasterLayer.Raster;
    //Create classfy renderer and QI RasterRenderer interface
    IRasterClassifyColorRampRenderer pClassRen = new RasterClassifyColorRampRendererClass();
    IRasterRenderer pRasRen = pClassRen as IRasterRenderer;
    pRasRen.Raster = pRaster;
    //字串5
    //Set raster for the render and update
    pClassRen.ClassCount = NumOfClass;
    pRasRen.Update();
    // Create a color ramp to use
    IAlgorithmicColorRamp pRamp = new AlgorithmicColorRamp();
    pRamp.Size = NumOfClass;
    IRgbColor pFColor = new RgbColorClass();
    IRgbColor pTColor = new RgbColorClass();
    pFColor.NullColor = true;
    pTColor.RGB = 100;
    pRamp.FromColor = pFColor;
    pRamp.ToColor = pTColor;
    bool ok = true;
    pRamp.CreateRamp(out ok);
    // Create symbol for the classes 字串2
    IFillSymbol pFSymbol = new SimpleFillSymbolClass();
    //Update the renderer and plug into layer
    pFSymbol.Color = pFColor;
    ISymbol pSmbol1 = pFSymbol as ISymbol;
    pClassRen.set_Symbol(0, pSmbol1);
    pFSymbol.Color = pTColor;
    ISymbol pSmbol2 = pFSymbol as ISymbol;
    pClassRen.set_Symbol(1, pSmbol2);
    pRasRen.Update();
    pRasterLayer.Renderer = pClassRen as IRasterRenderer;
}