Clip Raster with Polygon with GDAL C++ - c++

Question

I am trying to clip a raster using a polygon an GDAL. At the moment i get an error that there is a read access violation when initializing the WarpOperation. I can access my Shapefile and check the num of features so the access is fine i think. Also i can access my Raster Data (GetProjectionRef).. All files are in the same CRS. Is there a way to use GdalWarp with Cutline?
const char* inputPath = "input.tif";
const char* outputPath = "output.tif";
//clipper Polygon
auto w_read_filenamePoly = "Polygon.shp";
char* read_filenamePoly = new char[w_read_filenamePoly.length() + 1];
wcstombs(read_filenamePoly, w_read_filenamePoly.c_str(), w_read_filenamePoly.length() + 1);
GDALDataset* hSrcDS;
GDALDataset* hDstDS;
GDALAllRegister();
hSrcDS =(GDALDataset *) GDALOpen(inputPath, GA_Update);
hDstDS = (GDALDataset*)GDALOpen(outputPath, GA_Update);
const char* proj = hSrcDS->GetProjectionRef();
const char* proj2 = hDstDS->GetProjectionRef();
//clipper Layer
GDALDataset* poDSClipper;
poDSClipper = (GDALDataset*)GDALOpenEx(read_filenamePoly, GDAL_OF_UPDATE, NULL, NULL, NULL);
Assert::IsNotNull(poDSClipper);
delete[]read_filenamePoly;
OGRLayer* poLayerClipper;
poLayerClipper = poDSClipper->GetLayerByName("Polygon");
int numClip = poLayerClipper->GetFeatureCount();
//setup warp options
GDALWarpOptions* psWarpOptions = GDALCreateWarpOptions();
psWarpOptions->hSrcDS = hSrcDS;
psWarpOptions->hDstDS = hDstDS;
psWarpOptions->nBandCount = 1;
psWarpOptions->panSrcBands = (int *) CPLMalloc(sizeof(int) * psWarpOptions->nBandCount);
psWarpOptions->panSrcBands[0] = 1;
psWarpOptions->panDstBands = (int*)CPLMalloc(sizeof(int) * psWarpOptions->nBandCount);
psWarpOptions->panDstBands[0] = 1;
psWarpOptions->pfnProgress = GDALTermProgress;
psWarpOptions->hCutline = poLayerClipper;
// Establish reprojection transformer.
psWarpOptions->pTransformerArg = GDALCreateGenImgProjTransformer(hSrcDS,proj, hDstDS, proj2, FALSE, 0.0, 1);
psWarpOptions->pfnTransformer = GDALGenImgProjTransform;
GDALWarpOperation oOperation;
oOperation.Initialize(psWarpOptions);
oOperation.ChunkAndWarpImage(0, 0, GDALGetRasterXSize(hDstDS), GDALGetRasterYSize(hDstDS));
GDALDestroyGenImgProjTransformer(psWarpOptions->pTransformerArg);
GDALDestroyWarpOptions(psWarpOptions);
GDALClose(hDstDS);
GDALClose(hSrcDS);

Answer 1

Your psWarpOptions->hCutline should be a polygon, not a layer.
Also the cutline should be in source pixel/line coordinates.
Check TransformCutlineToSource from gdalwarp_lib.cpp, you can probably simply get the code from there.
This particular GDAL operation, when called from C++, is so full of pitfalls - and there are so many open questions about it here - that I am reproducing a full working example:
Warping (reprojecting) a raster image with a polygon mask (cutline):
#include <gdal/gdal.h>
#include <gdal/gdal_priv.h>
#include <gdal/gdalwarper.h>
#include <gdal/ogrsf_frmts.h>
int main() {
const char *inputPath = "input.tif";
const char *outputPath = "output.tif";
// clipper Polygon
// THIS FILE MUST BE IN PIXEL/LINE COORDINATES or otherwise one should
// copy the function gdalwarp_lib.cpp:TransformCutlineToSource()
// from GDAL's sources
// It is expected that it contains a single polygon feature
const char *read_filenamePoly = "cutline.json";
GDALDataset *hSrcDS;
GDALDataset *hDstDS;
GDALAllRegister();
auto poDriver = GetGDALDriverManager()->GetDriverByName("GTiff");
hSrcDS = (GDALDataset *)GDALOpen(inputPath, GA_ReadOnly);
hDstDS = (GDALDataset *)poDriver->CreateCopy(
outputPath, hSrcDS, 0, nullptr, nullptr, nullptr);
// Without this step the cutline is useless - because the background
// will be carried over from the original image
CPLErr e = hDstDS->GetRasterBand(1)->Fill(0);
const char *src_srs = hSrcDS->GetProjectionRef();
const char *dst_srs = hDstDS->GetProjectionRef();
// clipper Layer
GDALDataset *poDSClipper;
poDSClipper = (GDALDataset *)GDALOpenEx(
read_filenamePoly, GDAL_OF_UPDATE, NULL, NULL, NULL);
auto poLayerClipper = poDSClipper->GetLayer(0);
auto geom = poLayerClipper->GetNextFeature()->GetGeometryRef();
// setup warp options
GDALWarpOptions *psWarpOptions = GDALCreateWarpOptions();
psWarpOptions->hSrcDS = hSrcDS;
psWarpOptions->hDstDS = hDstDS;
psWarpOptions->nBandCount = 1;
psWarpOptions->panSrcBands =
(int *)CPLMalloc(sizeof(int) * psWarpOptions->nBandCount);
psWarpOptions->panSrcBands[0] = 1;
psWarpOptions->panDstBands =
(int *)CPLMalloc(sizeof(int) * psWarpOptions->nBandCount);
psWarpOptions->panDstBands[0] = 1;
psWarpOptions->pfnProgress = GDALTermProgress;
psWarpOptions->hCutline = geom;
// Establish reprojection transformer.
psWarpOptions->pTransformerArg = GDALCreateGenImgProjTransformer(
hSrcDS, src_srs, hDstDS, dst_srs, TRUE, 1000, 1);
psWarpOptions->pfnTransformer = GDALGenImgProjTransform;
GDALWarpOperation oOperation;
oOperation.Initialize(psWarpOptions);
oOperation.ChunkAndWarpImage(
0, 0, GDALGetRasterXSize(hDstDS), GDALGetRasterYSize(hDstDS));
GDALDestroyGenImgProjTransformer(psWarpOptions->pTransformerArg);
GDALDestroyWarpOptions(psWarpOptions);
GDALClose(hDstDS);
GDALClose(hSrcDS);
}