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To warp a raster file to match the spatial reference, resolution, and extent of another raster file in C++ and output a VRT (Virtual Raster) file, you can use the GDAL (Geospatial Data Abstraction Library) library. GDAL provides a powerful set of tools for raster and vector data manipulation.
Here's a step-by-step guide to achieve this:
Install GDAL: Make sure GDAL is installed on your system. You can download it from the GDAL website or install it using a package manager like apt
on Linux or brew
on macOS.
Include GDAL in Your Project: Ensure that your C++ project is set up to include the GDAL headers and link against the GDAL library.
Write the C++ Code: Below is an example of how you can warp a raster file to match another raster file and output a VRT file.
#include <gdal_priv.h>
#include <cpl_conv.h> // for CPLMalloc()
int main(int argc, char **argv) {
if (argc < 4) {
printf("Usage: %s <source_raster> <reference_raster> <output_vrt>\n", argv[0]);
return 1;
}
const char *srcFilename = argv[1];
const char *refFilename = argv[2];
const char *dstFilename = argv[3];
GDALAllRegister();
// Open the source raster
GDALDataset *srcDataset = (GDALDataset *) GDALOpen(srcFilename, GA_ReadOnly);
if (srcDataset == nullptr) {
printf("Failed to open source raster: %s\n", srcFilename);
return 1;
}
// Open the reference raster
GDALDataset *refDataset = (GDALDataset *) GDALOpen(refFilename, GA_ReadOnly);
if (refDataset == nullptr) {
printf("Failed to open reference raster: %s\n", refFilename);
GDALClose(srcDataset);
return 1;
}
// Get the spatial reference, resolution, and extent from the reference raster
double refGeoTransform[6];
refDataset->GetGeoTransform(refGeoTransform);
const char *refProjection = refDataset->GetProjectionRef();
int refXSize = refDataset->GetRasterXSize();
int refYSize = refDataset->GetRasterYSize();
// Set up the warp options
GDALWarpOptions *warpOptions = GDALCreateWarpOptions();
warpOptions->hSrcDS = srcDataset;
warpOptions->hDstDS = nullptr; // We will create the VRT dataset later
warpOptions->nBandCount = srcDataset->GetRasterCount();
warpOptions->panSrcBands = (int *) CPLMalloc(sizeof(int) * warpOptions->nBandCount);
warpOptions->panDstBands = (int *) CPLMalloc(sizeof(int) * warpOptions->nBandCount);
for (int i = 0; i < warpOptions->nBandCount; i++) {
warpOptions->panSrcBands[i] = i + 1;
warpOptions->panDstBands[i] = i + 1;
}
// Create the VRT dataset
GDALDriver *vrtDriver = GetGDALDriverManager()->GetDriverByName("VRT");
GDALDataset *vrtDataset = vrtDriver->Create(dstFilename, refXSize, refYSize, 0, GDT_Unknown, nullptr);
vrtDataset->SetGeoTransform(refGeoTransform);
vrtDataset->SetProjection(refProjection);
// Set the destination dataset in the warp options
warpOptions->hDstDS = vrtDataset;
// Perform the warp
GDALWarpOperation warpOperation;
warpOperation.Initialize(warpOptions);
CPLErr err = warpOperation.ChunkAndWarpImage(0, 0, refXSize, refYSize);
if (err != CE_None) {
printf("Warping failed.\n");
}
// Clean up
GDALDestroyWarpOptions(warpOptions);
GDALClose(srcDataset);
GDALClose(refDataset);
GDALClose(vrtDataset);
return (err == CE_None) ? 0 : 1;
}
GDALAllRegister()
registers all GDAL drivers.GDALOpen()
opens the source and reference raster files.GetGeoTransform()
, GetProjectionRef()
, GetRasterXSize()
, and GetRasterYSize()
retrieve the spatial reference, resolution, and extent of the reference raster.GDALCreateWarpOptions()
creates warp options, and we set the source and destination bands.GetGDALDriverManager()->GetDriverByName("VRT")
gets the VRT driver, and Create()
creates the VRT dataset with the same properties as the reference raster.GDALWarpOperation
performs the warp operation.GDALDestroyWarpOptions()
, GDALClose()
clean up resources.Make sure to link against the GDAL library when compiling your code. For example:
g++ -o warp_raster warp_raster.cpp -lgdal
This example assumes you have basic knowledge of C++ and GDAL. Adjust paths and error handling as needed for your specific use case.