AE 空间参考与用矢量图剪裁栅格图

    做GIS二次开发，不论用什么语言或二次开发工具，只要对图形的操作，都会涉及到空间参考的问题，至于空间参考的基础知识我就不再强调了！在做栅格裁剪的时候，也会涉及到空间参考的问题，主要有一下几个地方，有栅格图的空间参考、矢量图的空间参考、剪裁后栅格图的空间参考，最好这三个参考是一致的，如果不一致就要让他一致，以下为例子代码：pRaster为原栅格图，pPolygon为矢量图的上的某个面要素的最大外环。以原栅格图为参考基准。重点在于投影空间参考！

  //多边形裁剪 、矩形裁剪
        public  void CutByPolygon(ILayer layer, IGeometry clipGeo,string m_Path,string m_CutType)
        {
            IRasterLayer pRasterLayer = layer as IRasterLayer;
            IRaster pRaster = pRasterLayer.Raster;
            IRasterProps pProps = pRaster as IRasterProps;
            object cellSizeProvider = pProps.MeanCellSize().X;
            IGeoDataset pInputDataset = pRaster as IGeoDataset;
            //修改矢量图要素空间参考
            clipGeo.Project(pInputDataset.SpatialReference);
           
            IExtractionOp pExtractionOp = new RasterExtractionOpClass();
            IRasterAnalysisEnvironment pRasterAnaEnvir = pExtractionOp as IRasterAnalysisEnvironment;
            pRasterAnaEnvir.SetCellSize(esriRasterEnvSettingEnum.esriRasterEnvValue, ref cellSizeProvider);          
            object extentProvider = clipGeo.Envelope;
            object snapRasterData = Type.Missing;
            pRasterAnaEnvir.SetExtent(esriRasterEnvSettingEnum.esriRasterEnvValue, ref extentProvider, ref snapRasterData);
            //投影栅格空间参考
            rstAnalysisEnvironment.OutSpatialReference = pProps.SpatialReference;
            IGeoDataset pOutputDataset = null;
            switch (m_CutType)
            {
                case "多边形裁剪":
                    pOutputDataset = pExtractionOp.Polygon(pInputDataset, clipGeo as IPolygon, true);
                    break;
                case "矩形裁剪":
                    pOutputDataset = pExtractionOp.Rectangle(pInputDataset, clipGeo.Envelope  as IEnvelope, true);
                    break;
            }

            IRaster clipRaster;  //裁切后得到的IRaster
            if (pOutputDataset is IRasterLayer)
            {
                IRasterLayer rasterLayer = pOutputDataset as IRasterLayer;
                clipRaster = rasterLayer.Raster;
            }
            else if (pOutputDataset is IRasterDataset)
            {
                IRasterDataset rasterDataset = pOutputDataset as IRasterDataset;
                clipRaster = rasterDataset.CreateDefaultRaster();
            }
            else if (pOutputDataset is IRaster)
            {
                clipRaster = pOutputDataset as IRaster;
                //增加阈值设定
                IRasterProps temRastPro = clipRaster as IRasterProps;
                temRastPro.NoDataValue = pProps.NoDataValue;
                temRastPro.PixelType = pProps.PixelType;
            }
            else
            {
                return;
            }
            //保存新裁剪结果
            string wpath = System.IO.Path.GetDirectoryName(m_Path);

            string wname = System.IO.Path.GetFileName(m_Path);
            string wtpype = System.IO.Path.GetExtension(m_Path);
            string pFormat = "TIFF";
            switch (wtpype)
            {
                case ".bmp":
                    pFormat = "BMP";
                    break;
                case ".tiff":
                case ".tif":
                    pFormat = "TIFF";
                    break;
                case ".img":
                    pFormat = "IMAGINE Image";
                    break;
                case ".jpg":
                    pFormat = "JPG";
                    break;
            }
            IWorkspaceFactory pWKSF = new RasterWorkspaceFactoryClass();
            IWorkspace pWorkspace = pWKSF.OpenFromFile(wpath, 0);
            ISaveAs2 pSaveAs = clipRaster as ISaveAs2;
            pSaveAs.SaveAs(wname, pWorkspace, pFormat);
            MessageBox.Show("影像裁切完成！！！", "消息提示");
            
        }

 还有一种方法，但不建议使用，就是彻底修改矢量图的空间参考：

  /// <summary>
        /// 改变图层的空间参考
        /// </summary>
        /// <param name="pFeatureLayer">图层</param>
        /// <param name="pGeoType">空间参考类型</param>
        private void ChangeLayerRef(IFeatureLayer pFeatureLayer, ISpatialReference pSRF)
        {
            try
            {
                IFeatureClass pFeatureClass = pFeatureLayer.FeatureClass;
                //QI到IGeoDataset
                IGeoDataset pGeoDataset = pFeatureClass as IGeoDataset;
                //ISchemaLock schemaLock = (ISchemaLock)pGeoDataset;
                //schemaLock.ChangeSchemaLock(esriSchemaLock.esriExclusiveSchemaLock);
                //QI到IGeoDatasetSchemaEdit
                IGeoDatasetSchemaEdit pGeoDatasetSchemaEdit = pGeoDataset as IGeoDatasetSchemaEdit;
                if (pGeoDatasetSchemaEdit.CanAlterSpatialReference)
                {
                    ////创建SpatialReferenceEnvironmentClass对象
                    //ISpatialReferenceFactory2 pSpaRefFactory = new SpatialReferenceEnvironmentClass();
                    ////创建地理坐标系对象
                    //IGeographicCoordinateSystem pNewGeoSys = pSpaRefFactory.CreateGeographicCoordinateSystem(gcsType);//4214代表Beijing1954
                    //pGeoDatasetSchemaEdit.AlterSpatialReference(pNewGeoSys);
                    pGeoDatasetSchemaEdit.AlterSpatialReference(pSRF);
                }
            }
            catch (Exception Err)
            {
                MessageBox.Show(Err.Message, "提示", MessageBoxButtons.OK, MessageBoxIcon.Information);
            }
        }