为镶嵌数据集批量创建快视图

镶嵌数据集(Mosaic Dataset)是ArcGIS 10.0中推出的一种全新的空间数据模型,用于管理海量影像数据。我们经常需要访问影像数据的快视图,本文将为您介绍如何批量地为镶嵌数据集创建快视图文件。

环境说明:本例采用的是File Geodatabase,即文件地理数据库来存储镶嵌数据集;使用ArcObjects开发,以ArcGIS Add-In的方式部署在ArcMap中,作为一个命令工具使用。下图是工具的界面设计:


可以看到该工具实现功能需要经过几个关键步骤:

1.用户点击选择按钮,打开文件夹浏览对话框,选择File Geodatabase;

2.程序自动访问File Geodatabase,并获取其中所有的Mosaic Dataset,放到下拉框列表中供用户选择;

3.用户设置其他输出参数:快视图存储路径、DPI、图片压缩比等;

4.用户点击“开始生成”按钮,执行批量创建快视图任务;

5.程序提示当前创建内容,显示进度,完成后提示用户。

其中最为关键的是用户点击开始生成按钮后的操作,包括访问镶嵌数据集,遍历其中每一景影像数据,并为其创建快视图。

以下是点击按钮执行的代码:

        private void btnCreate_Click(object sender, EventArgs e)
        {
            if (txtGdbPath.Text.Trim() == "" || Directory.Exists(txtGdbPath.Text) == false ||
                txtPreviewPath.Text.Trim() == "" || Directory.Exists(txtPreviewPath.Text) == false)
            {
                MessageBox.Show("请选择正确的空间数据库和快视图目录!");
                return;
            }

            txtLog.Text += "开始:详细进度信息将写入日志文件。\r\n";
            long start = DateTime.Now.Ticks;
            LogHelper.AddMessage(string.Format("{0} 开始执行快视图生成操作...", DateTime.Now.ToLongTimeString()));
            //打开镶嵌数据集
            IMosaicDataset md = GdbHelper.OpenMosaicDataset(_workspace, cmbDatasets.SelectedItem.ToString());
            if (md == null)
            {
                txtLog.Text += "错误:未获取到镶嵌数据集,请查看日志了解详细信息。\r\n";
                return;
            }

            short quality = (short)numQuality.Value;
            int dpi = (int)numDpi.Value;
            //批量创建快视图
            GdbHelper.CreatePreview(md, _activeView, cmbDatasets.SelectedItem.ToString(), txtPreviewPath.Text, quality, dpi);

            long end = DateTime.Now.Ticks;
            int totalTime = (int)((end - start) / TimeSpan.TicksPerSecond);
            LogHelper.AddMessage(string.Format("{0} 快视图生成操作完成,共计用时{1}秒。", DateTime.Now.ToLongTimeString(), totalTime));

            LogHelper.WriteToLogFile();
            txtLog.Text += "完成:请查看日志了解详细信息。";
        }

以下是遍历镶嵌数据集的代码:

        public static void CreatePreview(IMosaicDataset mosaicDataset, IActiveView view, string mdName, string dirPreview, short quality, int outRes)
        {
            ITable pTable = GetMosaicDatasetTable(mosaicDataset);
            if (pTable == null) return;

            int indexName = pTable.FindField("NAME");
            int indexOID = pTable.FindField("OBJECTID");
            int indexRaster = pTable.FindField("RASTER");

            ICursor pCursor = pTable.Search(null, false);
            IRow pRow = pCursor.NextRow();

            int count = 1;
            while (pRow != null)
            {
                string rasterName = Convert.ToString(pRow.get_Value(indexName));
                string oid = Convert.ToString(pRow.get_Value(indexOID));
                string picName = string.Format("{0}_{1}.jpg", mdName, oid);
                picName = System.IO.Path.Combine(dirPreview, picName);

                LogHelper.AddMessage(string.Format("正在创建第 {0} 个快视图:{1}...", count, picName));

                if (File.Exists(picName))
                {
                    LogHelper.AddMessage(string.Format("{0} 已存在,跳过...", picName));
                }
                else                    
                {
                    try
                    {
                        IRasterCatalogItem pRasterCatalogItem = (IRasterCatalogItem)pRow;
                        IRasterDataset pRasterdataset = pRasterCatalogItem.RasterDataset;

                        IRasterLayer pRasterlayer = new RasterLayerClass();
                        pRasterlayer.CreateFromDataset(pRasterdataset);

                        IRaster pRaster = pRasterlayer.Raster;
                        IRasterProps pRasterpro = pRaster as IRasterProps;

                        if (view.FocusMap.LayerCount > 0)
                        {
                            view.FocusMap.ClearLayers();
                        }
                        view.FocusMap.AddLayer(pRasterlayer as ILayer);

                        IArea pArea = pRasterpro.Extent.Envelope as IArea;
                        view.FullExtent = pRasterpro.Extent;
                        view.FullExtent.CenterAt(pArea.Centroid);
                        view.Refresh();
                        view.FocusMap.RecalcFullExtent();

                        ExportActiveView(view, picName, pRasterpro.Extent, quality, outRes);
                    }
                    catch (Exception ex)
                    {
                        LogHelper.AddMessage(string.Format("为 {0} 创建快视图失败:", ex.Message));
                    }
                }

                pRow = pCursor.NextRow();
                count++;

                if (count % 100 == 0)
                {
                    LogHelper.WriteToLogFile();
                    GC.Collect();//如不清理内存,将导致内存占用过大,x64系统达到3.8G左右程序无响应
                }
            }

            Marshal.ReleaseComObject(pCursor);

            view.Clear();
        }

以下是创建快视图的代码:

        private static void ExportActiveView(ESRI.ArcGIS.Carto.IActiveView pActiveView, System.String picName, IEnvelope pEn, short quality, int outRes)
        {
            if (pActiveView == null || !(picName.EndsWith(".jpg"))) return;

            ESRI.ArcGIS.Output.IExport export = new ESRI.ArcGIS.Output.ExportJPEGClass();
            export.ExportFileName = picName;
            export.Resolution = outRes;//输出分辨率,即DPI,默认96

            IExportJPEG pEXG = export as IExportJPEG;
            pEXG.Quality = quality;//图片质量,0~100,100表示不压缩

            tagRECT exportRECT; // This is a structure
            exportRECT.right = pActiveView.ExportFrame.right;
            exportRECT.bottom = pActiveView.ExportFrame.bottom;
            exportRECT = pActiveView.ExportFrame;

            IDisplayTransformation pDisplayTransformation = pActiveView.ScreenDisplay.DisplayTransformation;
            pDisplayTransformation.TransformRect(pEn, ref exportRECT, 8);

            exportRECT.left = 0;
            exportRECT.top = 0;

            //isc
            //Set up the PixelBounds envelope to match the exportRECT
            ESRI.ArcGIS.Geometry.IEnvelope envelope = new ESRI.ArcGIS.Geometry.EnvelopeClass();
            envelope.PutCoords(exportRECT.left, exportRECT.top, exportRECT.right, exportRECT.bottom);
            export.PixelBounds = envelope;

            System.Int32 hDC = export.StartExporting();

            pActiveView.Output(hDC, (System.Int16)export.Resolution, ref exportRECT, pEn, null); // Explicit Cast and 'ref' keyword needed 
            export.FinishExporting();
            export.Cleanup();
            pActiveView.Clear();

            Marshal.ReleaseComObject(pEXG);
            Marshal.ReleaseComObject(export);

            pEXG = null;
            export = null;
        }

以上就是为镶嵌数据集批量创建快视图的关键代码,如需完整代码,请在评论中留下邮箱地址,若有疑问,也请在评论中提出。

转载自:https://blog.csdn.net/esrichinacd/article/details/8935458

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