GDAL影像重采样
学习过程中，用到重采样，感觉不错，转载过来供大家学习，原文地址：http://blog.csdn.net/giselite/article/details/7792620
#include "gdal_priv.h"
#include "ogrsf_frmts.h"
#include "gdalwarper.h"
/***
* 遥感影像重采样 (要求影像必须有投影，否则走不通)
* @param pszSrcFile 输入文件的路径
* @param pszOutFile 写入的结果图像的路径
* @param eResample 采样模式，有五种，具体参见GDALResampleAlg定义，默认为双线性内插
* @param fResX X转换采样比，默认大小为1.0，大于1图像变大，小于1表示图像缩小。数值上等于采样后图像的宽度和采样前图像宽度的比
* @param fResY Y转换采样比，默认大小为1.0，大于1图像变大，小于1表示图像缩小。数值上等于采样后图像的高度和采样前图像高度的比
* @retrieve 0 成功
* @retrieve -1 打开源文件失败
* @retrieve -2 创建新文件失败
* @retrieve -3 处理过程中出错
*/
int ResampleGDAL(const char* pszSrcFile, const char* pszOutFile, float fResX = 1.0 ,float fResY = 1.0,GDALResampleAlg eResample = GRA_Bilinear)
{
GDALAllRegister();
CPLSetConfigOption("GDAL_FILENAME_IS_UTF8","NO");
GDALDataset *pDSrc = (GDALDataset *)GDALOpen(pszSrcFile, GA_ReadOnly);
if (pDSrc == NULL)
{
return -1;
}
GDALDriver *pDriver = GetGDALDriverManager()->GetDriverByName("GTiff");
if (pDriver == NULL)
{
GDALClose((GDALDatasetH) pDSrc);
return -2;
}
int width=pDSrc->GetRasterXSize();
int height=pDSrc->GetRasterYSize();
int nBandCount = pDSrc->GetRasterCount();
GDALDataType dataType = pDSrc->GetRasterBand(1)->GetRasterDataType();
char *pszSrcWKT = NULL;
pszSrcWKT = const_cast<char *>(pDSrc->GetProjectionRef());
//如果没有投影，人为设置一个
if(strlen(pszSrcWKT)<=0)
{
OGRSpatialReference oSRS;
oSRS.SetUTM(50,true); //北半球 东经120度
oSRS.SetWellKnownGeogCS("WGS84");
oSRS.exportToWkt(&pszSrcWKT);
}
void *hTransformArg;
hTransformArg = GDALCreateGenImgProjTransformer((GDALDatasetH) pDSrc,pszSrcWKT,NULL,pszSrcWKT,FALSE,0.0,1);
//(没有投影的影像到这里就走不通了)
if (hTransformArg == NULL)
{
GDALClose((GDALDatasetH) pDSrc);
return -3;
}
double dGeoTrans[6] = {0};
int nNewWidth=0,nNewHeight=0;
if(GDALSuggestedWarpOutput((GDALDatasetH)pDSrc,GDALGenImgProjTransform,hTransformArg,dGeoTrans,&nNewWidth,&nNewHeight)!=CE_None)
{
GDALClose((GDALDatasetH) pDSrc);
return -3;
}
GDALDestroyGenImgProjTransformer(hTransformArg);
//adfGeoTransform[0] /* top left x */
//adfGeoTransform[1] /* w-e pixel resolution */
//adfGeoTransform[2] /* rotation, 0 if image is "north up" */
//adfGeoTransform[3] /* top left y */
//adfGeoTransform[4] /* rotation, 0 if image is "north up" */
//adfGeoTransform[5] /* n-s pixel resolution */
dGeoTrans[1] = dGeoTrans[1] / fResX;
dGeoTrans[5] = dGeoTrans[5] / fResY;
nNewWidth = static_cast<int>(nNewWidth*fResX+0.5);
nNewHeight = static_cast<int>(nNewHeight*fResY+0.5);
//创建结果数据集
GDALDataset *pDDst = pDriver->Create(pszOutFile, nNewWidth, nNewHeight, nBandCount, dataType, NULL);
if (pDDst == NULL)
{
GDALClose((GDALDatasetH) pDSrc);
return -2;
}
pDDst->SetProjection(pszSrcWKT);
pDDst->SetGeoTransform(dGeoTrans);
GDALWarpOptions *psWo = GDALCreateWarpOptions();
//psWo->papszWarpOptions = CSLDuplicate(NULL);
psWo->eWorkingDataType = dataType;
psWo->eResampleAlg = eResample;
psWo->hSrcDS = (GDALDatasetH) pDSrc;
psWo->hDstDS = (GDALDatasetH) pDDst;
psWo->pfnTransformer = GDALGenImgProjTransform;
psWo->pTransformerArg = GDALCreateGenImgProjTransformer((GDALDatasetH) pDSrc,pszSrcWKT,(GDALDatasetH) pDDst,pszSrcWKT,FALSE,0.0,1);;
psWo->nBandCount = nBandCount;
psWo->panSrcBands = (int *) CPLMalloc(nBandCount*sizeof(int));
psWo->panDstBands = (int *) CPLMalloc(nBandCount*sizeof(int));
for (int i=0; i<nBandCount; i++)
{
psWo->panSrcBands[i] = i+1;
psWo->panDstBands[i] = i+1;
}
GDALWarpOperation oWo;
if (oWo.Initialize(psWo) != CE_None)
{
GDALClose((GDALDatasetH) pDSrc);
GDALClose((GDALDatasetH) pDDst);
return -3;
}
oWo.ChunkAndWarpImage(0, 0, nNewWidth, nNewHeight);
GDALFlushCache( pDDst );
GDALDestroyGenImgProjTransformer(psWo->pTransformerArg);
GDALDestroyWarpOptions( psWo );
GDALClose((GDALDatasetH) pDSrc);
GDALClose((GDALDatasetH) pDDst);
return 0;
} 用法示例：
ResampleGDAL("F:\\Work\\\\数据\\spline.tif",
"F:\\Work\\数据\\Resample_Lanczos.tif",GRA_Lanczos,10,10);
ResampleGDAL("F:\\Work\\数据\\test.tif",
"F:\\Work\\数据\\Resample3.tif",GRA_Lanczos,3,3);
缺陷：没有投影就不能重采样，关键点在于：GDALCreateGenImgProjTransformer取到的是null，根据gdal源代码，如果没有投影，dGeoTrans[] = {0,1,0,0,0,1},这个时候GDALCreateGenImgProjTransformer就返回null，因此可以将dGeoTrans[0]或dGeoTrans[3]设置为非0，这样GDALCreateGenImgProjTransformer就不返回null了。
改进：
/***
* 遥感影像重采样
* @param pszSrcFile 输入文件的路径
* @param pszOutFile 写入的结果图像的路径
* @param eResample 采样模式，有五种，具体参见GDALResampleAlg定义，默认为双线性内插
GRA_NearestNeighbour=0 最近邻法，算法简单并能保持原光谱信息不变；缺点是几何精度差，灰度不连续，边缘会出现锯齿状
GRA_Bilinear=1 双线性法，计算简单，图像灰度具有连续性且采样精度比较精确；缺点是会丧失细节；
GRA_Cubic=2 三次卷积法，计算量大，图像灰度具有连续性且采样精度高；
GRA_CubicSpline=3 三次样条法，灰度连续性和采样精度最佳；
GRA_Lanczos=4 分块兰索斯法，由匈牙利数学家、物理学家兰索斯法创立，实验发现效果和双线性接近；
* @param fResX X转换采样比，默认大小为1.0，大于1图像变大，小于1表示图像缩小。数值上等于采样后图像的宽度和采样前图像宽度的比
* @param fResY Y转换采样比，默认大小为1.0，大于1图像变大，小于1表示图像缩小。数值上等于采样后图像的高度和采样前图像高度的比
* @retrieve 0 成功
* @retrieve -1 打开源文件失败
* @retrieve -2 创建新文件失败
* @retrieve -3 处理过程中出错
*/
int ResampleGDAL(const char* pszSrcFile, const char* pszOutFile, float fResX = 1.0 ,float fResY = 1.0,GDALResampleAlg eResample = GRA_Bilinear)
{
GDALAllRegister();
CPLSetConfigOption("GDAL_FILENAME_IS_UTF8","NO");
GDALDataset *pDSrc = (GDALDataset *)GDALOpen(pszSrcFile, GA_ReadOnly);
if (pDSrc == NULL)
{
return -1;
}
GDALDriver *pDriver = GetGDALDriverManager()->GetDriverByName("GTiff");
if (pDriver == NULL)
{
GDALClose((GDALDatasetH) pDSrc);
return -2;
}
int width=pDSrc->GetRasterXSize();
int height=pDSrc->GetRasterYSize();
int nBandCount = pDSrc->GetRasterCount();
GDALDataType dataType = pDSrc->GetRasterBand(1)->GetRasterDataType();
char *pszSrcWKT = NULL;
pszSrcWKT = const_cast<char *>(pDSrc->GetProjectionRef());
double dGeoTrans[6] = {0};
int nNewWidth=width,nNewHeight=height;
pDSrc->GetGeoTransform(dGeoTrans);
bool bNoGeoRef = false;
double dOldGeoTrans0 = dGeoTrans[0];
//如果没有投影，人为设置一个
if(strlen(pszSrcWKT)<=0)
{
//OGRSpatialReference oSRS;
//oSRS.SetUTM(50,true); //北半球 东经120度
//oSRS.SetWellKnownGeogCS("WGS84");
//oSRS.exportToWkt(&pszSrcWKT);
//pDSrc->SetProjection(pszSrcWKT);
//////////////////////////////////////////////////////////////////////////
dGeoTrans[0]=1.0;
pDSrc->SetGeoTransform(dGeoTrans);
//////////////////////////////////////////////////////////////////////////
bNoGeoRef = true;
}
//adfGeoTransform[0] /* top left x */
//adfGeoTransform[1] /* w-e pixel resolution */
//adfGeoTransform[2] /* rotation, 0 if image is "north up" */
//adfGeoTransform[3] /* top left y */
//adfGeoTransform[4] /* rotation, 0 if image is "north up" */
//adfGeoTransform[5] /* n-s pixel resolution */
dGeoTrans[1] = dGeoTrans[1] / fResX;
dGeoTrans[5] = dGeoTrans[5] / fResY;
nNewWidth = static_cast<int>(nNewWidth*fResX+0.5);
nNewHeight = static_cast<int>(nNewHeight*fResY+0.5);
//创建结果数据集
GDALDataset *pDDst = pDriver->Create(pszOutFile, nNewWidth, nNewHeight, nBandCount, dataType, NULL);
if (pDDst == NULL)
{
GDALClose((GDALDatasetH) pDSrc);
return -2;
}
pDDst->SetProjection(pszSrcWKT);
pDDst->SetGeoTransform(dGeoTrans);
void *hTransformArg = NULL;
hTransformArg = GDALCreateGenImgProjTransformer2((GDALDatasetH) pDSrc, (GDALDatasetH) pDDst, NULL); //GDALCreateGenImgProjTransformer((GDALDatasetH) pDSrc,pszSrcWKT,(GDALDatasetH) pDDst,pszSrcWKT,FALSE,0.0,1);
if (hTransformArg == NULL)
{
GDALClose((GDALDatasetH) pDSrc);
GDALClose((GDALDatasetH) pDDst);
return -3;
}
GDALWarpOptions *psWo = GDALCreateWarpOptions();
psWo->papszWarpOptions = CSLDuplicate(NULL);
psWo->eWorkingDataType = dataType;
psWo->eResampleAlg = eResample;
psWo->hSrcDS = (GDALDatasetH) pDSrc;
psWo->hDstDS = (GDALDatasetH) pDDst;
psWo->pfnTransformer = GDALGenImgProjTransform;
psWo->pTransformerArg = hTransformArg;
psWo->nBandCount = nBandCount;
psWo->panSrcBands = (int *) CPLMalloc(nBandCount*sizeof(int));
psWo->panDstBands = (int *) CPLMalloc(nBandCount*sizeof(int));
for (int i=0; i<nBandCount; i++)
{
psWo->panSrcBands[i] = i+1;
psWo->panDstBands[i] = i+1;
}
GDALWarpOperation oWo;
if (oWo.Initialize(psWo) != CE_None)
{
GDALClose((GDALDatasetH) pDSrc);
GDALClose((GDALDatasetH) pDDst);
return -3;
}
oWo.ChunkAndWarpImage(0, 0, nNewWidth, nNewHeight);
GDALDestroyGenImgProjTransformer(hTransformArg);
GDALDestroyWarpOptions( psWo );
if(bNoGeoRef)
{
dGeoTrans[0]=dOldGeoTrans0;
pDDst->SetGeoTransform(dGeoTrans);
//pDDst->SetProjection("");
}
GDALFlushCache( pDDst );
GDALClose((GDALDatasetH) pDSrc);
GDALClose((GDALDatasetH) pDDst);
return 0;
} 改进后：没有投影也可以过去，但是如果没有投影，输出结果会自动带上一个投影，并且这个投影信息去不掉。
转载自：https://blog.csdn.net/sunj92/article/details/51787856
