Ejemplo n.º 1
0
int GDALDefaultOverviews::GetMaskFlags( int nBand )

{
/* -------------------------------------------------------------------- */
/*      Fetch this band's metadata entry.  They are of the form:        */
/*        INTERNAL_MASK_FLAGS_n: flags                                  */
/* -------------------------------------------------------------------- */
    if( !HaveMaskFile() )
        return 0;

    const char *pszValue =
        poMaskDS->GetMetadataItem(
            CPLString().Printf( "INTERNAL_MASK_FLAGS_%d", MAX(nBand,1)) );

    if( pszValue == NULL )
        return 0x8000;

    return atoi(pszValue);
}
Ejemplo n.º 2
0
CPLErr GDALDefaultOverviews::CreateMaskBand( int nFlags, int nBand )

{
    if( nBand < 1 )
        nFlags |= GMF_PER_DATASET;

/* -------------------------------------------------------------------- */
/*      ensure existing file gets opened if there is one.               */
/* -------------------------------------------------------------------- */
    CPL_IGNORE_RET_VAL(HaveMaskFile());

/* -------------------------------------------------------------------- */
/*      Try creating the mask file.                                     */
/* -------------------------------------------------------------------- */
    if( poMaskDS == NULL )
    {
        GDALDriver * const poDr =
            static_cast<GDALDriver *>( GDALGetDriverByName( "GTiff" ) );

        if( poDr == NULL )
            return CE_Failure;

        GDALRasterBand * const poTBand = poDS->GetRasterBand(1);
        if( poTBand == NULL )
            return CE_Failure;

        const int nBands = nFlags & GMF_PER_DATASET ?
            1 : poDS->GetRasterCount();

        char **papszOpt = CSLSetNameValue( NULL, "COMPRESS", "DEFLATE" );
        papszOpt = CSLSetNameValue( papszOpt, "INTERLEAVE", "BAND" );

        int nBX = 0;
        int nBY = 0;
        poTBand->GetBlockSize( &nBX, &nBY );

        // Try to create matching tile size if legal in TIFF.
        if( (nBX % 16) == 0 && (nBY % 16) == 0 )
        {
            papszOpt = CSLSetNameValue( papszOpt, "TILED", "YES" );
            papszOpt = CSLSetNameValue( papszOpt, "BLOCKXSIZE",
                                        CPLString().Printf("%d",nBX) );
            papszOpt = CSLSetNameValue( papszOpt, "BLOCKYSIZE",
                                        CPLString().Printf("%d",nBY) );
        }

        CPLString osMskFilename;
        osMskFilename.Printf( "%s.msk", poDS->GetDescription() );
        poMaskDS = poDr->Create( osMskFilename,
                                 poDS->GetRasterXSize(),
                                 poDS->GetRasterYSize(),
                                 nBands, GDT_Byte, papszOpt );
        CSLDestroy( papszOpt );

        if( poMaskDS == NULL )  // Presumably error already issued.
            return CE_Failure;

        bOwnMaskDS = true;
    }

/* -------------------------------------------------------------------- */
/*      Save the mask flags for this band.                              */
/* -------------------------------------------------------------------- */
    if( nBand > poMaskDS->GetRasterCount() )
    {
        CPLError( CE_Failure, CPLE_AppDefined,
                  "Attempt to create a mask band for band %d of %s, "
                  "but the .msk file has a PER_DATASET mask.",
                  nBand, poDS->GetDescription() );
        return CE_Failure;
    }

    for( int iBand = 0; iBand < poDS->GetRasterCount(); iBand++ )
    {
        // we write only the info for this band, unless we are
        // using PER_DATASET in which case we write for all.
        if( nBand != iBand + 1 && !(nFlags & GMF_PER_DATASET) )
            continue;

        poMaskDS->SetMetadataItem(
            CPLString().Printf("INTERNAL_MASK_FLAGS_%d", iBand+1 ),
            CPLString().Printf("%d", nFlags ) );
    }

    return CE_None;
}
Ejemplo n.º 3
0
CPLErr
GDALDefaultOverviews::BuildOverviews(
    const char * pszBasename,
    const char * pszResampling,
    int nOverviews, int * panOverviewList,
    int nBands, int * panBandList,
    GDALProgressFunc pfnProgress, void * pProgressData)

{
    if( pfnProgress == NULL )
        pfnProgress = GDALDummyProgress;

    if( nOverviews == 0 )
        return CleanOverviews();

/* -------------------------------------------------------------------- */
/*      If we don't already have an overview file, we need to decide    */
/*      what format to use.                                             */
/* -------------------------------------------------------------------- */
    if( poODS == NULL )
    {
        bOvrIsAux = CPLTestBool(CPLGetConfigOption( "USE_RRD", "NO" ));
        if( bOvrIsAux )
        {
            osOvrFilename = CPLResetExtension(poDS->GetDescription(),"aux");

            VSIStatBufL sStatBuf;
            if( VSIStatExL( osOvrFilename, &sStatBuf,
                            VSI_STAT_EXISTS_FLAG ) == 0 )
                osOvrFilename.Printf( "%s.aux", poDS->GetDescription() );
        }
    }
/* -------------------------------------------------------------------- */
/*      If we already have the overviews open, but they are             */
/*      read-only, then try and reopen them read-write.                 */
/* -------------------------------------------------------------------- */
    else if( poODS->GetAccess() == GA_ReadOnly )
    {
        GDALClose( poODS );
        poODS = static_cast<GDALDataset *>(
            GDALOpen( osOvrFilename, GA_Update ));
        if( poODS == NULL )
            return CE_Failure;
    }

/* -------------------------------------------------------------------- */
/*      Our TIFF overview support currently only works safely if all    */
/*      bands are handled at the same time.                             */
/* -------------------------------------------------------------------- */
    if( !bOvrIsAux && nBands != poDS->GetRasterCount() )
    {
        CPLError( CE_Failure, CPLE_NotSupported,
                  "Generation of overviews in external TIFF currently only "
                  "supported when operating on all bands.  "
                  "Operation failed." );
        return CE_Failure;
    }

/* -------------------------------------------------------------------- */
/*      If a basename is provided, use it to override the internal      */
/*      overview filename.                                              */
/* -------------------------------------------------------------------- */
    if( pszBasename == NULL && osOvrFilename.length() == 0  )
        pszBasename = poDS->GetDescription();

    if( pszBasename != NULL )
    {
        if( bOvrIsAux )
            osOvrFilename.Printf( "%s.aux", pszBasename );
        else
            osOvrFilename.Printf( "%s.ovr", pszBasename );
    }

/* -------------------------------------------------------------------- */
/*      Establish which of the overview levels we already have, and     */
/*      which are new.  We assume that band 1 of the file is            */
/*      representative.                                                 */
/* -------------------------------------------------------------------- */
    GDALRasterBand *poBand = poDS->GetRasterBand( 1 );

    int nNewOverviews = 0;
    int *panNewOverviewList = static_cast<int *>(
        CPLCalloc(sizeof(int), nOverviews) );
    double dfAreaNewOverviews = 0;
    double dfAreaRefreshedOverviews = 0;
    for( int i = 0; i < nOverviews && poBand != NULL; i++ )
    {
        for( int j = 0; j < poBand->GetOverviewCount(); j++ )
        {
            GDALRasterBand * poOverview = poBand->GetOverview( j );
            if( poOverview == NULL )
                continue;

            int nOvFactor =
                GDALComputeOvFactor(poOverview->GetXSize(),
                                    poBand->GetXSize(),
                                    poOverview->GetYSize(),
                                    poBand->GetYSize());

            if( nOvFactor == panOverviewList[i]
                || nOvFactor == GDALOvLevelAdjust2( panOverviewList[i],
                                                   poBand->GetXSize(),
                                                   poBand->GetYSize() ) )
            {
                panOverviewList[i] *= -1;
            }
        }

        const double dfArea = 1.0 / (panOverviewList[i] * panOverviewList[i]);
        dfAreaRefreshedOverviews += dfArea;
        if( panOverviewList[i] > 0 )
        {
            dfAreaNewOverviews += dfArea;
            panNewOverviewList[nNewOverviews++] = panOverviewList[i];
        }
    }

/* -------------------------------------------------------------------- */
/*      Build band list.                                                */
/* -------------------------------------------------------------------- */
    GDALRasterBand **pahBands = static_cast<GDALRasterBand **>(
        CPLCalloc(sizeof(GDALRasterBand *), nBands) );
    for( int i = 0; i < nBands; i++ )
        pahBands[i] = poDS->GetRasterBand( panBandList[i] );

/* -------------------------------------------------------------------- */
/*      Build new overviews - Imagine.  Keep existing file open if      */
/*      we have it.  But mark all overviews as in need of               */
/*      regeneration, since HFAAuxBuildOverviews() doesn't actually     */
/*      produce the imagery.                                            */
/* -------------------------------------------------------------------- */

    CPLErr eErr = CE_None;

    void* pScaledProgress = GDALCreateScaledProgress(
            0, dfAreaNewOverviews / dfAreaRefreshedOverviews,
            pfnProgress, pProgressData );
    if( bOvrIsAux )
    {
        if( nNewOverviews == 0 )
        {
            /* if we call HFAAuxBuildOverviews() with nNewOverviews == 0 */
            /* because that there's no new, this will wipe existing */
            /* overviews (#4831) */
            // eErr = CE_None;
        }
        else
        {
            eErr = HFAAuxBuildOverviews( osOvrFilename, poDS, &poODS,
                                     nBands, panBandList,
                                     nNewOverviews, panNewOverviewList,
                                     pszResampling,
                                     GDALScaledProgress, pScaledProgress );
        }
        for( int j = 0; j < nOverviews; j++ )
        {
            if( panOverviewList[j] > 0 )
                panOverviewList[j] *= -1;
        }
    }

/* -------------------------------------------------------------------- */
/*      Build new overviews - TIFF.  Close TIFF files while we          */
/*      operate on it.                                                  */
/* -------------------------------------------------------------------- */
    else
    {
        if( poODS != NULL )
        {
            delete poODS;
            poODS = NULL;
        }

        eErr = GTIFFBuildOverviews( osOvrFilename, nBands, pahBands,
                                    nNewOverviews, panNewOverviewList,
                                    pszResampling,
                                    GDALScaledProgress, pScaledProgress );

        // Probe for proxy overview filename.
        if( eErr == CE_Failure )
        {
            const char *pszProxyOvrFilename =
                poDS->GetMetadataItem("FILENAME","ProxyOverviewRequest");

            if( pszProxyOvrFilename != NULL )
            {
                osOvrFilename = pszProxyOvrFilename;
                eErr = GTIFFBuildOverviews( osOvrFilename, nBands, pahBands,
                                            nNewOverviews, panNewOverviewList,
                                            pszResampling,
                                            GDALScaledProgress, pScaledProgress );
            }
        }

        if( eErr == CE_None )
        {
            poODS = static_cast<GDALDataset *>(
                GDALOpen( osOvrFilename, GA_Update ) );
            if( poODS == NULL )
                eErr = CE_Failure;
        }
    }

    GDALDestroyScaledProgress( pScaledProgress );

/* -------------------------------------------------------------------- */
/*      Refresh old overviews that were listed.                         */
/* -------------------------------------------------------------------- */
    GDALRasterBand **papoOverviewBands = static_cast<GDALRasterBand **>(
        CPLCalloc(sizeof(void*), nOverviews) );

    for( int iBand = 0; iBand < nBands && eErr == CE_None; iBand++ )
    {
        poBand = poDS->GetRasterBand( panBandList[iBand] );

        nNewOverviews = 0;
        for( int i = 0; i < nOverviews && poBand != NULL; i++ )
        {
            for( int j = 0; j < poBand->GetOverviewCount(); j++ )
            {
                GDALRasterBand * poOverview = poBand->GetOverview( j );
                if( poOverview == NULL )
                    continue;

                int bHasNoData = FALSE;
                double noDataValue = poBand->GetNoDataValue(&bHasNoData);

                if( bHasNoData )
                  poOverview->SetNoDataValue(noDataValue);

                const int nOvFactor =
                    GDALComputeOvFactor(poOverview->GetXSize(),
                                        poBand->GetXSize(),
                                        poOverview->GetYSize(),
                                        poBand->GetYSize());

                if( nOvFactor == - panOverviewList[i]
                    || (panOverviewList[i] < 0 &&
                        nOvFactor == GDALOvLevelAdjust2( -panOverviewList[i],
                                                       poBand->GetXSize(),
                                                       poBand->GetYSize() )) )
                {
                    papoOverviewBands[nNewOverviews++] = poOverview;
                    break;
                }
            }
        }

        if( nNewOverviews > 0 )
        {
            const double dfOffset = dfAreaNewOverviews / dfAreaRefreshedOverviews;
            const double dfScale = 1.0 - dfOffset;
            pScaledProgress = GDALCreateScaledProgress(
                    dfOffset + dfScale * iBand / nBands,
                    dfOffset + dfScale * (iBand+1) / nBands,
                    pfnProgress, pProgressData );
            eErr = GDALRegenerateOverviews( (GDALRasterBandH) poBand,
                                            nNewOverviews,
                                            (GDALRasterBandH*)papoOverviewBands,
                                            pszResampling,
                                            GDALScaledProgress, pScaledProgress );
            GDALDestroyScaledProgress( pScaledProgress );
        }
    }

/* -------------------------------------------------------------------- */
/*      Cleanup                                                         */
/* -------------------------------------------------------------------- */
    CPLFree( papoOverviewBands );
    CPLFree( panNewOverviewList );
    CPLFree( pahBands );

/* -------------------------------------------------------------------- */
/*      If we have a mask file, we need to build its overviews too.     */
/* -------------------------------------------------------------------- */
    if( HaveMaskFile() && poMaskDS )
    {
        // Some config option are not compatible with mask overviews
        // so unset them, and define more sensible values.
        const bool bJPEG =
            EQUAL(CPLGetConfigOption("COMPRESS_OVERVIEW", ""), "JPEG");
        const bool bPHOTOMETRIC_YCBCR =
            EQUAL(CPLGetConfigOption("PHOTOMETRIC_OVERVIEW", ""), "YCBCR");
        if( bJPEG )
            CPLSetThreadLocalConfigOption("COMPRESS_OVERVIEW", "DEFLATE");
        if( bPHOTOMETRIC_YCBCR )
            CPLSetThreadLocalConfigOption("PHOTOMETRIC_OVERVIEW", "");

        poMaskDS->BuildOverviews( pszResampling, nOverviews, panOverviewList,
                                  0, NULL, pfnProgress, pProgressData );

        // Restore config option.
        if( bJPEG )
            CPLSetThreadLocalConfigOption("COMPRESS_OVERVIEW", "JPEG");
        if( bPHOTOMETRIC_YCBCR )
            CPLSetThreadLocalConfigOption("PHOTOMETRIC_OVERVIEW", "YCBCR");

        if( bOwnMaskDS )
        {
            // Reset the poMask member of main dataset bands, since it
            // will become invalid after poMaskDS closing.
            for( int iBand = 1; iBand <= poDS->GetRasterCount(); iBand ++ )
            {
                GDALRasterBand *poOtherBand = poDS->GetRasterBand(iBand);
                if( poOtherBand != NULL )
                    poOtherBand->InvalidateMaskBand();
            }

            GDALClose( poMaskDS );
        }

        // force next request to reread mask file.
        poMaskDS = NULL;
        bOwnMaskDS = false;
        bCheckedForMask = false;
    }

/* -------------------------------------------------------------------- */
/*      If we have an overview dataset, then mark all the overviews     */
/*      with the base dataset  Used later for finding overviews         */
/*      masks.  Uggg.                                                   */
/* -------------------------------------------------------------------- */
    if( poODS )
    {
        const int nOverviewCount = GetOverviewCount(1);

        for( int iOver = 0; iOver < nOverviewCount; iOver++ )
        {
            GDALRasterBand *poOtherBand = GetOverview( 1, iOver );
            GDALDataset *poOverDS = poOtherBand != NULL ?
                poOtherBand->GetDataset() : NULL;

            if( poOverDS != NULL )
            {
                poOverDS->oOvManager.poBaseDS = poDS;
                poOverDS->oOvManager.poDS = poOverDS;
            }
        }
    }

    return eErr;
}
CPLErr
GDALDefaultOverviews::BuildOverviews( 
    const char * pszBasename,
    const char * pszResampling, 
    int nOverviews, int * panOverviewList,
    int nBands, int * panBandList,
    GDALProgressFunc pfnProgress, void * pProgressData)

{
    GDALRasterBand **pahBands;
    CPLErr       eErr;
    int          i;

    if( pfnProgress == NULL )
        pfnProgress = GDALDummyProgress;

    if( nOverviews == 0 )
        return CleanOverviews();

/* -------------------------------------------------------------------- */
/*      If we don't already have an overview file, we need to decide    */
/*      what format to use.                                             */
/* -------------------------------------------------------------------- */
    if( poODS == NULL )
    {
        bOvrIsAux = CSLTestBoolean(CPLGetConfigOption( "USE_RRD", "NO" ));
        if( bOvrIsAux )
        {
            VSIStatBufL sStatBuf;

            osOvrFilename = CPLResetExtension(poDS->GetDescription(),"aux");

            if( VSIStatL( osOvrFilename, &sStatBuf ) == 0 )
                osOvrFilename.Printf( "%s.aux", poDS->GetDescription() );
        }
    }
/* -------------------------------------------------------------------- */
/*      If we already have the overviews open, but they are             */
/*      read-only, then try and reopen them read-write.                 */
/* -------------------------------------------------------------------- */
    else if( poODS->GetAccess() == GA_ReadOnly )
    {
        GDALClose( poODS );
        poODS = (GDALDataset *) GDALOpen( osOvrFilename, GA_Update );
        if( poODS == NULL )
            return CE_Failure;
    }

/* -------------------------------------------------------------------- */
/*      Our TIFF overview support currently only works safely if all    */
/*      bands are handled at the same time.                             */
/* -------------------------------------------------------------------- */
    if( !bOvrIsAux && nBands != poDS->GetRasterCount() )
    {
        CPLError( CE_Failure, CPLE_NotSupported,
                  "Generation of overviews in external TIFF currently only"
                  " supported when operating on all bands.\n" 
                  "Operation failed.\n" );
        return CE_Failure;
    }

/* -------------------------------------------------------------------- */
/*      If a basename is provided, use it to override the internal      */
/*      overview filename.                                              */
/* -------------------------------------------------------------------- */
    if( pszBasename == NULL && osOvrFilename.length() == 0  )
        pszBasename = poDS->GetDescription();

    if( pszBasename != NULL )
    {
        if( bOvrIsAux )
            osOvrFilename.Printf( "%s.aux", pszBasename );
        else
            osOvrFilename.Printf( "%s.ovr", pszBasename );
    }

/* -------------------------------------------------------------------- */
/*      Establish which of the overview levels we already have, and     */
/*      which are new.  We assume that band 1 of the file is            */
/*      representative.                                                 */
/* -------------------------------------------------------------------- */
    int   nNewOverviews, *panNewOverviewList = NULL;
    GDALRasterBand *poBand = poDS->GetRasterBand( 1 );

    nNewOverviews = 0;
    panNewOverviewList = (int *) CPLCalloc(sizeof(int),nOverviews);
    for( i = 0; i < nOverviews && poBand != NULL; i++ )
    {
        int   j;

        for( j = 0; j < poBand->GetOverviewCount(); j++ )
        {
            int    nOvFactor;
            GDALRasterBand * poOverview = poBand->GetOverview( j );
 
            nOvFactor = (int) 
                (0.5 + poBand->GetXSize() / (double) poOverview->GetXSize());

            if( nOvFactor == panOverviewList[i] 
                || nOvFactor == GDALOvLevelAdjust( panOverviewList[i], 
                                                   poBand->GetXSize() ) )
                panOverviewList[i] *= -1;
        }

        if( panOverviewList[i] > 0 )
            panNewOverviewList[nNewOverviews++] = panOverviewList[i];
    }

/* -------------------------------------------------------------------- */
/*      Build band list.                                                */
/* -------------------------------------------------------------------- */
    pahBands = (GDALRasterBand **) CPLCalloc(sizeof(GDALRasterBand *),nBands);
    for( i = 0; i < nBands; i++ )
        pahBands[i] = poDS->GetRasterBand( panBandList[i] );

/* -------------------------------------------------------------------- */
/*      Build new overviews - Imagine.  Keep existing file open if      */
/*      we have it.  But mark all overviews as in need of               */
/*      regeneration, since HFAAuxBuildOverviews() doesn't actually     */
/*      produce the imagery.                                            */
/* -------------------------------------------------------------------- */

#ifndef WIN32CE

    if( bOvrIsAux )
    {
        eErr = HFAAuxBuildOverviews( osOvrFilename, poDS, &poODS,
                                     nBands, panBandList,
                                     nNewOverviews, panNewOverviewList, 
                                     pszResampling, 
                                     pfnProgress, pProgressData );

        int j;
        
        for( j = 0; j < nOverviews; j++ )
        {
            if( panOverviewList[j] > 0 )
                panOverviewList[j] *= -1;
        }
    }

/* -------------------------------------------------------------------- */
/*      Build new overviews - TIFF.  Close TIFF files while we          */
/*      operate on it.                                                  */
/* -------------------------------------------------------------------- */
    else
#endif /* WIN32CE */
    {
        if( poODS != NULL )
        {
            delete poODS;
            poODS = NULL;
        }

        eErr = GTIFFBuildOverviews( osOvrFilename, nBands, pahBands, 
                                    nNewOverviews, panNewOverviewList, 
                                    pszResampling, pfnProgress, pProgressData );
        
        // Probe for proxy overview filename. 
        if( eErr == CE_Failure )
        {
            const char *pszProxyOvrFilename = 
                poDS->GetMetadataItem("FILENAME","ProxyOverviewRequest");

            if( pszProxyOvrFilename != NULL )
            {
                osOvrFilename = pszProxyOvrFilename;
                eErr = GTIFFBuildOverviews( osOvrFilename, nBands, pahBands, 
                                            nNewOverviews, panNewOverviewList, 
                                            pszResampling, 
                                            pfnProgress, pProgressData );
            }
        }

        if( eErr == CE_None )
        {
            poODS = (GDALDataset *) GDALOpen( osOvrFilename, GA_Update );
            if( poODS == NULL )
                eErr = CE_Failure;
        }
    }

/* -------------------------------------------------------------------- */
/*      Refresh old overviews that were listed.                         */
/* -------------------------------------------------------------------- */
    GDALRasterBand **papoOverviewBands;

    papoOverviewBands = (GDALRasterBand **) 
        CPLCalloc(sizeof(void*),nOverviews);

    for( int iBand = 0; iBand < nBands && eErr == CE_None; iBand++ )
    {
        poBand = poDS->GetRasterBand( panBandList[iBand] );

        nNewOverviews = 0;
        for( i = 0; i < nOverviews && poBand != NULL; i++ )
        {
            int   j;
            
            for( j = 0; j < poBand->GetOverviewCount(); j++ )
            {
                int    nOvFactor;
                GDALRasterBand * poOverview = poBand->GetOverview( j );

                int bHasNoData;
                double noDataValue = poBand->GetNoDataValue(&bHasNoData);

                if (bHasNoData)
                  poOverview->SetNoDataValue(noDataValue);

                nOvFactor = (int) 
                    (0.5 + poBand->GetXSize() / (double) poOverview->GetXSize());

                if( nOvFactor == - panOverviewList[i] 
                    || nOvFactor == GDALOvLevelAdjust( -panOverviewList[i], 
                                                       poBand->GetXSize() ) )
                {
                    papoOverviewBands[nNewOverviews++] = poOverview;
                    break;
                }
            }
        }

        if( nNewOverviews > 0 )
        {
            eErr = GDALRegenerateOverviews( (GDALRasterBandH) poBand, 
                                            nNewOverviews, 
                                            (GDALRasterBandH*)papoOverviewBands,
                                            pszResampling, 
                                            pfnProgress, pProgressData );
        }
    }

/* -------------------------------------------------------------------- */
/*      Cleanup                                                         */
/* -------------------------------------------------------------------- */
    CPLFree( papoOverviewBands );
    CPLFree( panNewOverviewList );
    CPLFree( pahBands );

/* -------------------------------------------------------------------- */
/*      If we have a mask file, we need to build it's overviews         */
/*      too.                                                            */
/* -------------------------------------------------------------------- */
    if( HaveMaskFile() && poMaskDS )
    {
        poMaskDS->BuildOverviews( pszResampling, nOverviews, panOverviewList,
                                  0, NULL, pfnProgress, pProgressData );
        if( bOwnMaskDS )
            GDALClose( poMaskDS );

        // force next request to reread mask file.
        poMaskDS = NULL;
        bOwnMaskDS = FALSE;
        bCheckedForMask = FALSE;
    }

/* -------------------------------------------------------------------- */
/*      If we have an overview dataset, then mark all the overviews     */
/*      with the base dataset  Used later for finding overviews         */
/*      masks.  Uggg.                                                   */
/* -------------------------------------------------------------------- */
    if( poODS )
    {
        int nOverviewCount = GetOverviewCount(1);
        int iOver;

        for( iOver = 0; iOver < nOverviewCount; iOver++ )
        {
            GDALRasterBand *poBand = GetOverview( 1, iOver );
            GDALDataset    *poOverDS = NULL;

            if( poBand != NULL )
                poOverDS = poBand->GetDataset();

            if (poOverDS != NULL)
            {
                poOverDS->oOvManager.poBaseDS = poDS;
                poOverDS->oOvManager.poDS = poOverDS;
            }
        }
    }

    return eErr;
}