GDAL image resampling

#include "gdal_priv.h"
#include "ogrsf_frmts.h"
#include "gdalwarper.h"

/** *  Resampling function (GDAL) * @param pszSrcFile  Enter the path to the file  * @param pszOutFile  The path of the written result image  * @param fResX X Convert sampling ratio , The default size is 1.0, Greater than 1 The image becomes larger , Less than 1 Indicates that the image is reduced  * @param fResY Y Convert sampling ratio , The default size is 1.0 * @param nResampleMode  Sampling mode , There are five kinds of , Specific see GDALResampleAlg Definition , The default is bilinear interpolation  GRA_NearestNeighbour=0  Nearest neighbor method , The algorithm is simple and can keep the original spectral information unchanged ; The disadvantage is poor geometric accuracy , The gray scale is discontinuous , Jagged edges appear  GRA_Bilinear=1  Bilinear method , Simple calculation , The gray scale of the image is continuous and the sampling accuracy is relatively accurate ; The disadvantage is the loss of details ; GRA_Cubic=2  Cubic convolution , Large amount of computation , The gray scale of the image is continuous and the sampling accuracy is high ; GRA_CubicSpline=3  Cubic spline method , Gray continuity and sampling accuracy are the best ; GRA_Lanczos=4  Block Lanczos  , By Hungarian mathematicians 、 Physicist lanzos law founded , Experiments show that the effect is close to bilinear ; * @return 0  success ;-1  Failed to open source file ;-2  Failed to create new file ;-3  Error in processing  */
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");// Set the path to support Chinese 
	GDALDataset* pDSrc = (GDALDataset*)GDALOpen(pszSrcFile, GA_ReadOnly);
	if (pDSrc == NULL)
	{
    
		return -1;
	}


	GDALDriver* pDriver = GetGDALDriverManager()->GetDriverByName("GTiff");//  Set file type 
	if (pDriver == NULL)
	{
    
		GDALClose((GDALDatasetH)pDSrc);
		return -2;
	}
	int width = pDSrc->GetRasterXSize();//  Width 
	int height = pDSrc->GetRasterYSize();//  Height 
	int nBandCount = pDSrc->GetRasterCount();//  Band number 
	GDALDataType dataType = pDSrc->GetRasterBand(1)->GetRasterDataType();//  Grid data type 


	char* pszSrcWKT = NULL;
	pszSrcWKT = const_cast<char*>(pDSrc->GetProjectionRef()); //  Projection information 


	double dGeoTrans[6] = {
     0 };
	int nNewWidth = width, nNewHeight = height;
	pDSrc->GetGeoTransform(dGeoTrans); //  Affine transformation  

	//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 */

	// Calculate the image size after sampling 
	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);


	// Create a result dataset 
	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;//  Band number 
	psWo->panSrcBands = (int*)CPLMalloc(nBandCount * sizeof(int));//  The memory occupied by the number of bands of the input file 
	psWo->panDstBands = (int*)CPLMalloc(nBandCount * sizeof(int));//  Memory occupied by the number of bands of the output file 
	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);

	GDALFlushCache(pDDst);
	GDALClose((GDALDatasetH)pDSrc);
	GDALClose((GDALDatasetH)pDDst);


	return 0;
}

int main()
{
    
	ResampleGDAL(" data （ Test data ）/label_RGB.tif","test.tif", 0.5, 0.5, GRA_Bilinear);
}