栅格数据AE

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, 0);

2. 用IRasterDataset接口打开一个栅格数据集

IWorkspaceFactory workspaceFactory = new RasterWorkspaceFactory();
IWorkspace workspace;
workspace = workspaceFactory.OpenFromFile(inPath, 0); //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 = 0; i < dHeight; i++)
for (int j = 0; j < dWidth; j++)
{
pnt.SetCoords(i, j);
clipRaster.Read(pnt, pixelBlock);
if (pixelBlock != null)
{
object obj = pixelBlock.GetVal(0, 0, 0);
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, 0);// _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, 0);
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, 0);
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(0);
pRasterBand.ComputeStatsAndHist();
IRasterStatistics pRasterStatistic = pRasterBand.Statistics;
double dMaxValue = pRasterStatistic.Maximum ;
double dMinValue = pRasterStatistic.Minimum ;
INumberRemap pNumRemap = new NumberRemapClass();
pNumRemap.MapRange(dMinValue, 0, 0);
pNumRemap.MapRange(0, dMaxValue, 1);
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 = 0; 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 = 0; 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(0);
ITable pRTable = pBand.AttributeTable;
DataTable pTable = new DataTable();
for (int i = 0; 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 =0 ;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(0, 0);
// Create the dataset
IRasterWorkspace2 rasterWorkspace2 = null;
rasterWorkspace2 = CreateRasterWorkspace(directoryName);
rasterDataset = rasterWorkspace2.CreateRasterDataset(fileName, "IMAGINE Image", originPoint, 200, 100, 1, 1, 1, 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(0);
rasterProps = (IRasterProps)rawPixels;
// Create pixelblock
pixelBlockOrigin = new DblPntClass();
pixelBlockOrigin.SetCoords(0, 0);
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(0);
// Loop through all the pixels and assign value
for (int i = 0; i < rasterProps.Width; i++)
for (int j = 0; j < rasterProps.Height; j++)
pixelData[i, j] = (i * j) % 255;
// 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, 0) 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,0)as ITinWorkspace;
ITinAdvanced2 tinAd = TinWK.OpenTin(tinName) as ITinAdvanced2;
IEnvelope extent = tinAd.Extent;
IPoint origin = extent.LowerLeft;
origin.X = origin.X - (5 * 0.5);
origin.Y = origin.Y - (5 * 0.5);
int nCol = (int)Math.Round(extent.Width / 5) + 1;
int nRow = (int)Math.Round(extent.Height / 5) +1;
ISpatialReference2 spatialRef = (ISpatialReference2)extent.SpatialReference;
IWorkspaceFactory rasterWF = new RasterWorkspaceFactoryClass();
IRasterWorkspace2 workSpace = (IRasterWorkspace2)rasterWF.OpenFromFile(rasterPath,0);
rasterDataset = workSpace.CreateRasterDataset(gridName, "GRID", origin,nCol,nRow,5,5,1,ESRI.ArcGIS.Geodatabase.rstPixelType.PT_FLOAT, spatialRef,true);
IRasterBandCollection bandColl = (IRasterBandCollection) rasterDataset;
IRasterBand rasterBand = bandColl.Item(0);
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(0);
MessageBox.Show(val.ToString());
double cellsize = 5;
origin.X = origin.X + (5 * 0.5);
origin.Y = origin.Y + (5 * nRow) - (5 * 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 = 0;
offset.Y = 0;
rawPixels.Write(offset,pixelBlock as IPixelBlock);
}
catch(Exception ex)
{
MessageBox.Show(ex.ToString());
}
return rasterDataset;
}