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栅格数据AE

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11/25
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转自原文 栅格数据AE

两个星期以来一直与栅格数据打交道，对AO的栅格部分应该有了一定的理解，下面是自己的一点体会，希望高手指教：－）

1、栅格数据的存储类型

栅格数据一般可以存储为ESRI GRID（由一系列文件组成），TIFF格式（包括一个TIF文件和一个AUX文件），IMAGINE Image格式 在AE中一般调用ISaveAs接口来保存栅格数据

2、栅格数据集和栅格编目的区别

一个栅格数据集由一个或者多个波段（RasterBand）的数据组成，一个波段就是一个数据矩阵。对于格网数据（DEM数据）和单波段的影像数据，表现为仅仅只有一个波段数据的栅格数据集，而对于多光谱影像数据则表现为具有多个波段的栅格数据集

栅格编目（RasterCatalog）用于显示某个研究区域内各种相邻的栅格数据，这些相邻的栅格数据没有经过拼接处理合成一副大的影像图

3、IRasterWorkspaceEx与IRasterWorkspace ,IRsterWorkspace2的区别

1).IRasteWorkspaceEx接口主要是用来读取GeoDatabase中的栅格数据集和栅格编目

2) . IRasterWorkspace ,IRsterWorkspace2主要是用来读取以文件格式存储在本地的栅格数据

4、加载栅格数据（以存储在本地的栅格数据文件为例）

1.直接用IRasterLayer接口打开一个栅格文件并加载到地图控件 

IRasterLayer rasterLayer = new RasterLayerClass();

rasterLayer.CreateFromFilePath(fileName); // fileName指存本地的栅格文件路径

axMapControl1.AddLayer(rasterLayer, );

2. 用IRasterDataset接口打开一个栅格数据集 

IWorkspaceFactory workspaceFactory = new RasterWorkspaceFactory();

IWorkspace workspace;

workspace = workspaceFactory.OpenFromFile(inPath, ); //inPath栅格数据存储路径

if (workspace == null)

{

Console.WriteLine("Could not open the workspace.");

return;

}

IRasterWorkspace rastWork = (IRasterWorkspace)workspace;

IRasterDataset rastDataset;

rastDataset= rastWork.OpenRasterDataset(inName);//inName栅格文件名

if (rastDataset == null)

{

Console.WriteLine("Could not open the raster dataset.");

return;

}

5、如何读取栅格数据的属性和遍历栅格数据

栅格数据的属性包括栅格大小，行数，列数，投影信息，栅格范围等等，见下面代码

（假设当前加载的栅格文件栅格值存储方式为：UShort类型） 

IRasterProps rasterProps = (IRasterProps)clipRaster;

int dHeight = rasterProps.Height;//当前栅格数据集的行数

int dWidth = rasterProps.Width; //当前栅格数据集的列数

double dX = rasterProps.MeanCellSize().X; //栅格的宽度

double dY = rasterProps.MeanCellSize().Y; //栅格的高度

IEnvelope extent=rasterProps.Extent; //当前栅格数据集的范围

rstPixelType pixelType=rasterProps.PixelType; //当前栅格像素类型

IPnt pntSize = new PntClass();

pntSize.SetCoords(dX, dY);

IPixelBlock pixelBlock = clipRaster.CreatePixelBlock(pntSize);

IPnt pnt = new PntClass();

for (int i = ; i < dHeight; i++)

for (int j = ; j < dWidth; j++)

{

pnt.SetCoords(i, j);

clipRaster.Read(pnt, pixelBlock);

if (pixelBlock != null)

{

object obj = pixelBlock.GetVal(, , );

MessageBox.Show( Convert.ToUInt32(obj).ToString());

}

}

6、如何提取指定的范围的栅格数据

提取指定范围内的栅格数据通常用两种方法IRasterLayerExport(esriCarto), IExtractionOp, IExtractionOp2 (esriSpatialAnalyst)，IRasterLayerExport接口提供的栅格数据提取功能有限，只能以矩形范围作为提取范围，而IExtractionOp接口提供了多边形，圆，属性，矩形等几种形式作为提取栅格数据.

1).IRasterLayerExport接口 

IRasterLayerExport rLayerExport = new RasterLayerExportClass();

rLayerExport.RasterLayer = rasterLayer;// rasterLayer指当前加载的栅格图层

rLayerExport.Extent = clipExtent;//clipExtent指提取栅格数据的范围

if (proSpatialRef != null)

rLayerExport.SpatialReference = proSpatialRef;// proSpatialRef当前栅格数据的投影信息

IWorkspaceFactory pWF = new RasterWorkspaceFactoryClass();

try

{

IWorkspace pRasterWorkspace = pWF.OpenFromFile(_folder, );// _folder指栅格文件保存路径

IRasterDataset outGeoDataset = rLayerExport.Export(pRasterWorkspace, code, strRasterType);

//调用ISaveAs接口将导出的数据集保存

……………………..

}

Catch(Exception ex)

{

Throw new Argumention(ex.Message);

}

2)．IExtractionOp接口(调用此接口前，应该先检查空间许可) 

IExtractionOp extraction = new RasterExtractionOpClass();

try

{

IGeoDataset geoDataset = extraction.Rectangle((IGeoDataset)clipRaster, clipExtent, true);

IRaster raster = geoDataset as IRaster;

if (raster != null)

{

IWorkspaceFactory WF = new RasterWorkspaceFactoryClass();

IWorkspace rasterWorkspace = WF.OpenFromFile(_folder, );

ISaveAs saveAs = (ISaveAs)raster;

saveAs.SaveAs(“Result.tif”, rasterWorkspace, "TIFF");

}

}

catch (Exception ex)

{

MessageBox..Show(Ex.message);

}

7．栅格数据重采样

栅格数据的重采样主要基于三种方法：最邻近采样（NEAREST），双线性

ILINEAR）和三次卷积采样（CUBIC）。

（1）.最邻近采样：它用输入栅格数据中最临近栅格值作为输出值。因此，在重采

样后的输出栅格中的每个栅格值, 都是输入栅格数据中真实存在而未加任何改变的值。这种方法简单易用，计算量小，重采样的速度最快。

（2）.双线性采样：此重采样法取待采样点（x，y）点周围四个邻点，在y方向（或X方向）内插两次，再在x方向（或y方向）内插一次，得到（x，y）点的栅格值。

（3）.三次卷积采样：这是进一步提高内插精度的一种方法。它的基本思想是增加邻点来获

得最佳插值函数。取待计算点周围相邻的16个点，与双线性采样类似，可先在某一方向上内插，如先在x方向上，每四个值依次内插四次，再根据四次的计算结果在y方上内插，最终得到内插结果

代码示例：采用双线性采样 

IRasterGeometryProc rasterGeometryProc = new RasterGeometryProcClass();

rasterGeometryProc.Resample(rstResamplingTypes.RSP_CubicConvolution, newCellSize, clipRaster);

public static IRasterLayer SetViewShedRenderer(IRaster pInRaster,string sField,string sPath)

{

IRasterDescriptor pRD = new RasterDescriptorClass();

pRD.Create(pInRaster, new QueryFilterClass(), sField);

IReclassOp pReclassOp = new RasterReclassOpClass();

IGeoDataset pGeodataset=pInRaster as IGeoDataset;

IRasterAnalysisEnvironment pEnv = pReclassOp as IRasterAnalysisEnvironment;

IWorkspaceFactory pWSF=new RasterWorkspaceFactoryClass();

IWorkspace pWS = pWSF.OpenFromFile(sPath, );

pEnv.OutWorkspace = pWS;

object objSnap = null;

object objExtent = pGeodataset.Extent;

pEnv.SetExtent(esriRasterEnvSettingEnum.esriRasterEnvValue, ref objExtent, ref objSnap);

pEnv.OutSpatialReference = pGeodataset.SpatialReference;

IRasterLayer pRLayer = new RasterLayerClass();

IRasterBandCollection pRsBandCol = pGeodataset as IRasterBandCollection;

IRasterBand pRasterBand = pRsBandCol.Item();

pRasterBand.ComputeStatsAndHist();

IRasterStatistics pRasterStatistic = pRasterBand.Statistics;

double dMaxValue = pRasterStatistic.Maximum ;

double dMinValue = pRasterStatistic.Minimum ;

INumberRemap pNumRemap = new NumberRemapClass();

pNumRemap.MapRange(dMinValue, , );

pNumRemap.MapRange(, dMaxValue, );

IRemap pRemap = pNumRemap as IRemap;

IRaster pOutRaster = pReclassOp.ReclassByRemap(pGeodataset, pRemap, false) as IRaster ;

pRLayer.CreateFromRaster(pOutRaster);

return pRLayer;

}

栅格图层和矢量图层的属性表浏览 

if (pLyr is IFeatureLayer)

{

DataTable pTable = new DataTable();

IFeatureLayer pFealyr = pLyr as IFeatureLayer;

IFeatureClass pFCls = pFealyr.FeatureClass;

string shape = "";

if (pFCls.ShapeType == esriGeometryType.esriGeometryPoint)

shape = "Point";

else if (pFCls.ShapeType == esriGeometryType.esriGeometryPolyline)

shape = "Polyline";

else if (pFCls.ShapeType == esriGeometryType.esriGeometryPolygon)

shape = "Polygon";

for (int i = ; i < pFCls.Fields.FieldCount; i++)

{

pTable.Columns.Add(pFCls.Fields.get_Field(i).Name);

}

IFeatureCursor pCursor = pFCls.Search(null, false);

int ishape = pFCls.Fields.FindField("Shape");

IFeature pFea = pCursor.NextFeature();

while (pFea != null)

{

DataRow pRow = pTable.NewRow();

for (int i = ; i < pFCls.Fields.FieldCount; i++)

{

if (i == ishape)

{

pRow[i] = shape;

continue;

}

pRow[i] = pFea.get_Value(i).ToString();

}

pTable.Rows.Add(pRow);

pFea = pCursor.NextFeature();

}

dataGridView1.DataSource = pTable;

}

else if (pLyr is IRasterLayer)

{

IRasterLayer pRlyr = pLyr as IRasterLayer;

IRaster pRaster = pRlyr.Raster;

IRasterProps pProp = pRaster as IRasterProps;

pProp.PixelType = rstPixelType.PT_LONG;

if (pProp.PixelType == rstPixelType.PT_LONG)

{

IRasterBandCollection pBcol = pRaster as IRasterBandCollection;

IRasterBand pBand = pBcol.Item();

ITable pRTable = pBand.AttributeTable;

DataTable pTable = new DataTable();

for (int i = ; i < pRTable.Fields.FieldCount; i++)

pTable.Columns.Add(pRTable.Fields.get_Field(i).Name);

ICursor pCursor= pRTable.Search(null, false);

IRow pRrow= pCursor.NextRow();

while (pRrow != null)

{

DataRow pRow = pTable.NewRow();

for (int i = ;i<pRrow .Fields .FieldCount ;i++)

{

pRow[i] = pRrow.get_Value(i).ToString () ;

}

pTable.Rows.Add(pRow);

pRrow = pCursor.NextRow();

}

dataGridView1.DataSource = pTable;

}

}

创建栅格数据集 

CreateRasterDataset C#

public IRasterDataset CreateFileRasterDataset(string directoryName, string fileName)

{

// This function creates a new img file in the given workspace

// and then assigns pixel values

try

{

IRasterDataset rasterDataset = null;

IPoint originPoint = new PointClass();

originPoint.PutCoords(, );

// Create the dataset

IRasterWorkspace2 rasterWorkspace2 = null;

rasterWorkspace2 = CreateRasterWorkspace(directoryName);

rasterDataset = rasterWorkspace2.CreateRasterDataset(fileName, "IMAGINE Image", originPoint, , , , , , rstPixelType.PT_UCHAR, new UnknownCoordinateSystemClass(), true);

IRawPixels rawPixels = null;

IPixelBlock3 pixelBlock3 = null;

IPnt pixelBlockOrigin = null;

IPnt pixelBlockSize = null;

IRasterBandCollection rasterBandCollection;

IRasterProps rasterProps;

// QI for IRawPixels and IRasterProps

rasterBandCollection = (IRasterBandCollection)rasterDataset;

rawPixels = (IRawPixels)rasterBandCollection.Item();

rasterProps = (IRasterProps)rawPixels;

// Create pixelblock

pixelBlockOrigin = new DblPntClass();

pixelBlockOrigin.SetCoords(, );

pixelBlockSize = new DblPntClass();

pixelBlockSize.SetCoords(rasterProps.Width, rasterProps.Height);

pixelBlock3 = (IPixelBlock3)rawPixels.CreatePixelBlock(pixelBlockSize);

// Read pixelblock

rawPixels.Read(pixelBlockOrigin, (IPixelBlock)pixelBlock3);

// Get pixeldata array

System.Object[,] pixelData;

pixelData = (System.Object[,])pixelBlock3.get_PixelDataByRef();

// Loop through all the pixels and assign value

for (int i = ; i < rasterProps.Width; i++)

for (int j = ; j < rasterProps.Height; j++)

pixelData[i, j] = (i * j) % ;

// Write the pixeldata back

System.Object cachePointer;

cachePointer = rawPixels.AcquireCache();

rawPixels.Write(pixelBlockOrigin, (IPixelBlock)pixelBlock3);

rawPixels.ReturnCache(cachePointer);

// Return raster dataset

return rasterDataset;

}

catch (Exception ex)

{

System.Diagnostics.Debug.WriteLine(ex.Message);

return null;

}

}

public IRasterWorkspace2 CreateRasterWorkspace(string pathName)

{

// Create RasterWorkspace

IWorkspaceFactory workspaceFactory = new RasterWorkspaceFactoryClass();

return workspaceFactory.OpenFromFile(pathName, ) as IRasterWorkspace2;

}

public IRasterDataset tin2raster(string tempBathyTIN,string geoPath, string gridName)

{

string tinFolder = System.IO.Path.GetDirectoryName(tempBathyTIN);

string tinName = System.IO.Path.GetFileName(tempBathyTIN);

IRasterDataset rasterDataset = new RasterDatasetClass();

try

{

string rasterPath = System.IO.Path.GetDirectoryName(geoPath);

IWorkspaceFactory TinWF = new TinWorkspaceFactory();

ITinWorkspace TinWK = TinWF.OpenFromFile(tinFolder,)as ITinWorkspace;

ITinAdvanced2 tinAd = TinWK.OpenTin(tinName) as ITinAdvanced2;

IEnvelope extent = tinAd.Extent;

IPoint origin = extent.LowerLeft;

origin.X = origin.X - ( * 0.5);

origin.Y = origin.Y - ( * 0.5);

int nCol = (int)Math.Round(extent.Width / ) + ;

int nRow = (int)Math.Round(extent.Height / ) +;

ISpatialReference2 spatialRef = (ISpatialReference2)extent.SpatialReference;

IWorkspaceFactory rasterWF = new RasterWorkspaceFactoryClass();

IRasterWorkspace2 workSpace = (IRasterWorkspace2)rasterWF.OpenFromFile(rasterPath,);

rasterDataset = workSpace.CreateRasterDataset(gridName, "GRID", origin,nCol,nRow,,,,ESRI.ArcGIS.Geodatabase.rstPixelType.PT_FLOAT, spatialRef,true);

IRasterBandCollection bandColl = (IRasterBandCollection) rasterDataset;

IRasterBand rasterBand = bandColl.Item();

IRawPixels rawPixels = (IRawPixels)rasterBand;

IPnt blockSize = new DblPntClass();

blockSize.X = nCol;

blockSize.Y = nRow;

IPixelBlock3 pixelBlock = (IPixelBlock3)rawPixels.CreatePixelBlock(blockSize);

ITinSurface tinSurface = (ITinSurface)tinAd;

IRasterProps rasterProps = (IRasterProps)rawPixels;

object nodataFloat;

//long nodataInt;

object val = pixelBlock.get_PixelDataByRef();

MessageBox.Show(val.ToString());

double cellsize = ;

origin.X = origin.X + ( * 0.5);

origin.Y = origin.Y + ( * nRow) - ( * 0.5);

nodataFloat = Convert.ToDouble(rasterProps.NoDataValue.ToString());

tinSurface.QueryPixelBlock(origin.X,origin.Y,cellsize,cellsize,esriRasterizationType.esriElevationAsRaster,nodataFloat,val);

IPnt offset = new DblPntClass();

offset.X = ;

offset.Y = ;

rawPixels.Write(offset,pixelBlock as IPixelBlock);

}

catch(Exception ex)

{

MessageBox.Show(ex.ToString());

}

return rasterDataset;

}

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