gistfile1.mm

- (WarpResultC*)warpImageWithGeoTransform:(NSArray<NSNumber*>*)geoTransformArray sourceFile:(NSString*)inFilepath destinationFile:(NSString*)outFilepath
{
    GDALAllRegister();
    
    GDALDriverH hDriver;
    GDALDataType eDT;
    GDALDatasetH hDstDS;
    GDALDatasetH hSrcDS;
    
    // Open the source file.
    hSrcDS = GDALOpen( inFilepath.UTF8String, GA_ReadOnly );
    CPLAssert( hSrcDS != NULL );
    
    // Set the GeoTransform on the source image
    double geoTransform[] = { geoTransformArray[0].doubleValue, geoTransformArray[1].doubleValue, geoTransformArray[2].doubleValue, geoTransformArray[3].doubleValue, -geoTransformArray[4].doubleValue, -geoTransformArray[5].doubleValue };
    GDALSetGeoTransform(hSrcDS, geoTransform);
    
    // Create output with same datatype as first input band.
    eDT = GDALGetRasterDataType(GDALGetRasterBand(hSrcDS, 1));
    
    // Get output driver (GeoTIFF format)
    hDriver = GDALGetDriverByName( "GTiff" );
    CPLAssert( hDriver != NULL );
    
    // Create a transformer that maps from source pixel/line coordinates
    // to destination georeferenced coordinates (not destination
    // pixel line).  We do that by omitting the destination dataset
    // handle (setting it to NULL).
    void *hTransformArg = GDALCreateGenImgProjTransformer( hSrcDS, NULL, NULL, NULL, FALSE, 0, 1 );
    CPLAssert( hTransformArg != NULL );
    
    // Get approximate output georeferenced bounds and resolution for file.
    double adfDstGeoTransform[6];
    int nPixels=0, nLines=0;
    CPLErr eErr = GDALSuggestedWarpOutput( hSrcDS, GDALGenImgProjTransform, hTransformArg, adfDstGeoTransform, &nPixels, &nLines );
    CPLAssert( eErr == CE_None );
    GDALDestroyGenImgProjTransformer( hTransformArg );
    
    // Create the output file.
    hDstDS = GDALCreate( hDriver, outFilepath.UTF8String, nPixels, nLines, 4, eDT, NULL );
    CPLAssert( hDstDS != NULL );
    
    // Write out the projection definition.
    GDALSetGeoTransform( hDstDS, adfDstGeoTransform );
    
    // Copy the color table, if required.
    GDALColorTableH hCT = GDALGetRasterColorTable( GDALGetRasterBand(hSrcDS, 1) );
    if( hCT != NULL )
        GDALSetRasterColorTable( GDALGetRasterBand(hDstDS, 1), hCT );
    
    // Setup warp options.
    GDALWarpOptions *psWarpOptions = GDALCreateWarpOptions();
    psWarpOptions->hSrcDS = hSrcDS;
    psWarpOptions->hDstDS = hDstDS;
    
    /* -------------------------------------------------------------------- */
    /*      Do we have a source alpha band?                                 */
    /* -------------------------------------------------------------------- */
    bool enableSrcAlpha = GDALGetRasterColorInterpretation( GDALGetRasterBand(hSrcDS, GDALGetRasterCount(hSrcDS) )) == GCI_AlphaBand;
    if(enableSrcAlpha) { printf( "Using band %d of source image as alpha.\n", GDALGetRasterCount(hSrcDS) ); }
    
    /* -------------------------------------------------------------------- */
    /*      Setup band mapping.                                             */
    /* -------------------------------------------------------------------- */
    if(enableSrcAlpha)
        psWarpOptions->nBandCount = GDALGetRasterCount(hSrcDS) - 1;
    else
        psWarpOptions->nBandCount = GDALGetRasterCount(hSrcDS);
    
    psWarpOptions->panSrcBands = (int *) CPLMalloc(psWarpOptions->nBandCount*sizeof(int));
    psWarpOptions->panDstBands = (int *) CPLMalloc(psWarpOptions->nBandCount*sizeof(int));
    
    for( int i = 0; i < psWarpOptions->nBandCount; i++ )
    {
        psWarpOptions->panSrcBands[i] = i+1;
        psWarpOptions->panDstBands[i] = i+1;
    }
    
    /* -------------------------------------------------------------------- */
    /*      Setup alpha bands used if any.                                  */
    /* -------------------------------------------------------------------- */
    if( enableSrcAlpha )
        psWarpOptions->nSrcAlphaBand = GDALGetRasterCount(hSrcDS);

    psWarpOptions->nDstAlphaBand = GDALGetRasterCount(hDstDS);
    
    psWarpOptions->pfnProgress = GDALTermProgress;
    
    // Establish reprojection transformer.
    psWarpOptions->pTransformerArg = GDALCreateGenImgProjTransformer( hSrcDS, NULL, hDstDS, NULL, FALSE, 0.0, 1 );
    psWarpOptions->pfnTransformer = GDALGenImgProjTransform;
    
    // Initialize and execute the warp operation.
    GDALWarpOperation oOperation;
    oOperation.Initialize( psWarpOptions );
    CPLErr warpError = oOperation.ChunkAndWarpImage( 0, 0, GDALGetRasterXSize( hDstDS ), GDALGetRasterYSize( hDstDS ) );
    CPLAssert( warpError == CE_None );
    
    GDALDestroyGenImgProjTransformer( psWarpOptions->pTransformerArg );
    GDALDestroyWarpOptions( psWarpOptions );
    GDALClose( hDstDS );
    GDALClose( hSrcDS );
    
    WarpResultC* warpResultC = [WarpResultC new];
    warpResultC.geoTransformValues = @[@(adfDstGeoTransform[0]), @(adfDstGeoTransform[1]), @(adfDstGeoTransform[2]), @(adfDstGeoTransform[3]), @(adfDstGeoTransform[4]), @(adfDstGeoTransform[5])];
    warpResultC.newX = nPixels;
    warpResultC.newY = nLines;
    
    return warpResultC;
}