ArcEngine修改像素值与像元值

这里要注意的是单波段的栅格数据，比如dem一般是不能修改像素值的。而dem的像元值一般代表它的高程。这里的把我研究的高程数据的像元值全部改成了0和1。它要注意的是由于修改像素是直接在原数据上直接修改，所以完成后原数据就会没有了，所以大家可以先复制一下原数据再做。

一。改变栅格数据像素值

public void ChangeRasterValue(IRasterDataset2 pRasterDatset)
{
IRaster2 pRaster2 = pRasterDatset.CreateFullRaster() as IRaster2;
IPnt pPntBlock = new PntClass();

pPntBlock.X = 128;
pPntBlock.Y = 128;

IRasterCursor pRasterCursor = pRaster2.CreateCursorEx(pPntBlock);

IRasterEdit pRasterEdit = pRaster2 as IRasterEdit;
if (pRasterEdit.CanEdit())
{
IRasterBandCollection pBands = pRasterDatset as IRasterBandCollection;
IPixelBlock3 pPixelblock3 = null;
int pBlockwidth = 0;
int pBlockheight = 0;
System.Array pixels;
IPnt pPnt = null;
object pValue;
long pBandCount = pBands.Count;

//获取Nodata
//IRasterProps pRasterPro = pRaster2 as IRasterProps;

//object pNodata = pRasterPro.NoDataValue;
do
{
pPixelblock3 = pRasterCursor.PixelBlock as IPixelBlock3;
pBlockwidth = pPixelblock3.Width;
pBlockheight = pPixelblock3.Height;

for (int k = 0; k < pBandCount; k++)
{
pixels = (System.Array)pPixelblock3.get_PixelData(k);
for (int i = 0; i < pBlockwidth; i++)
{
for (int j = 0; j < pBlockheight; j++)
{
pValue = pixels.GetValue(i, j);

if (Convert.ToInt32(pValue) == 0 && isFlood[j, i] == true)
{
pixels.SetValue(Convert.ToByte(50), i, j);
}
}
}
pPixelblock3.set_PixelData(k, pixels);
}
pPnt = pRasterCursor.TopLeft;
pRasterEdit.Write(pPnt, (IPixelBlock)pPixelblock3);
}
while (pRasterCursor.Next());
System.Runtime.InteropServices.Marshal.ReleaseComObject(pRasterEdit);
MessageBox.Show("done");
}
}

还有就是根据IRaster2修改像素值

IRasterBandCollection rasterbands = (IRasterBandCollection)pRasterDataset;
IRasterBand rasterband = rasterbands.Item(0);
IRawPixels rawpixels = (IRawPixels)rasterbands.Item(0);
IRasterProps rasterpro = (IRasterProps)rasterband;

IRasterDataset2 rasterDataset2 = (IRasterDataset2)pRasterDataset;
IRaster raster = rasterDataset2.CreateFullRaster();
IRaster2 raster2 = (IRaster2)raster;

IPnt pBlockSize1 = new PntClass();
IEnvelope envelope = rasterpro.Extent;
pBlockSize1.SetCoords(envelope.Width, envelope.Height);

IPixelBlock pixelBlock = raster2.CreateCursorEx(pBlockSize1).PixelBlock;
int w = pixelBlock.Width;
int h = pixelBlock.Height;
//read the first pixel block
IPnt topleftCorner = new PntClass();
topleftCorner.SetCoords(0, 0);
raster.Read(topleftCorner, pixelBlock);
//modify one pixel value at location (assume the raster has a pixel type of uchar)
IPixelBlock3 pixelBlock3 = (IPixelBlock3)pixelBlock;
System.Array pixels = (System.Array)pixelBlock3.get_PixelData(0);
for (int finalX = 0; finalX < pRows; finalX++)
{
for (int finalY = 0; finalY < pColumns; finalY++)
{
if (isFlood[finalX, finalY] == true)
{
pixels.SetValue(Convert.ToByte(100), finalY, finalX);
}
//else
//{
//    pPixelData.SetValue(0, finalY, finalX);
//}
}
}
pixelBlock3.set_PixelData(0, (System.Object)pixels);
//write the modified pixel block to the raster dataset
IRasterEdit rasterEdit = (IRasterEdit)raster;
rasterEdit.Write(topleftCorner, pixelBlock);

二，栅格数据重分类，即修改栅格值

public void reclass(IRaster pRaster, double weight)
{
//int trueCount = 0;
//int falseCount = 0;
IRasterProps rasterProps = (IRasterProps)pRaster;
//设置栅格数据起始点
IPnt pBlockSize = new Pnt();
pBlockSize.SetCoords(rasterProps.Width, rasterProps.Height);
//获取整个范围
IPixelBlock pPixelBlock = pRaster.CreatePixelBlock(pBlockSize);
// IPixelBlock3 pPixelBlock = (IPixelBlock3)pRaster.CreatePixelBlock(pBlockSize);
//左上点坐标
IPnt tlp = new Pnt();
tlp.SetCoords(0, 0);
//读入栅格
IRasterBandCollection pRasterBands = pRaster as IRasterBandCollection;
IRasterBand pRasterBand = pRasterBands.Item(0);
IRawPixels pRawPixels = pRasterBands.Item(0) as IRawPixels;
pRawPixels.Read(tlp, pPixelBlock);
//将pixel的值组成数组
System.Array pSafeArray = pPixelBlock.get_SafeArray(0) as System.Array;
for (int y = 0; y < rasterProps.Height; y++)
{
for (int x = 0; x < rasterProps.Width; x++)
{
//int value = Convert.ToInt32(pSafeArray.GetValue(x, y));
//Byte value = Convert.ToByte(pSafeArray.GetValue(x, y));
//if (value != 0 && isFlood[y, x] == false)
//{
//    pSafeArray.SetValue((Byte)(value * weight), x, y);
//}
if (isFlood[y, x] == true)
{
pSafeArray.SetValue(1, x, y);
//trueCount++;
}
else
{
pSafeArray.SetValue(0, x, y);
//falseCount++;
}
}
}
pPixelBlock.set_SafeArray(0, pSafeArray);
//编辑raster,将更新的值写入raster中
IRasterEdit rasterEdit = pRaster as IRasterEdit;
rasterEdit.Write(tlp, pPixelBlock);
rasterEdit.Refresh();
int Fcount=0;
//m_map.AddLayer
//MessageBox.Show("ok");
//double result = Convert.ToDouble(pSafeArray.GetValue(100, 99));

}