tif_overview.c

TIFF文件格式读取及生成的源代码

                nXSize = MIN(nOMult,nBlockXSize-i);
                nYSize = MIN(nOMult,nBlockYSize-j);

                TIFF_GetSourceSamples( padfSamples, pabySrc, 
                                       nPixelBytes, nSampleFormat, 
                                       nXSize, nYSize, 
                                       nPixelGroupBytes, 
                                       nPixelGroupBytes * nBlockXSize );
                
                dfTotal = 0;
                for( iSample = 0; iSample < nXSize*nYSize; iSample++ )
                {
                    dfTotal += padfSamples[iSample];
                }

                TIFF_SetSample( pabyDst, nPixelBytes, nSampleFormat, 
                                dfTotal / (nXSize*nYSize) );

                pabySrc += nOMult * nPixelGroupBytes;
                pabyDst += nPixelBytes;
            }
        }
    }

    free( padfSamples );
}

/************************************************************************/
/*                      TIFF_ProcessFullResBlock()                      */
/*                                                                      */
/*      Process one block of full res data, downsampling into each      */
/*      of the overviews.                                               */
/************************************************************************/

void TIFF_ProcessFullResBlock( TIFF *hTIFF, int nPlanarConfig,
                               int nOverviews, int * panOvList,
                               int nBitsPerPixel, 
                               int nSamples, TIFFOvrCache ** papoRawBIs,
                               int nSXOff, int nSYOff,
                               unsigned char *pabySrcTile,
                               int nBlockXSize, int nBlockYSize,
                               int nSampleFormat, const char * pszResampling )
    
{
    int		iOverview, iSample;

    for( iSample = 0; iSample < nSamples; iSample++ )
    {
        /*
         * We have to read a tile/strip for each sample for
         * PLANARCONFIG_SEPARATE.  Otherwise, we just read all the samples
         * at once when handling the first sample.
         */
        if( nPlanarConfig == PLANARCONFIG_SEPARATE || iSample == 0 )
        {
            if( TIFFIsTiled(hTIFF) )
            {
                TIFFReadEncodedTile( hTIFF,
                                     TIFFComputeTile(hTIFF, nSXOff, nSYOff,
                                                     0, (tsample_t)iSample ),
                                     pabySrcTile,
                                     TIFFTileSize(hTIFF));
            }
            else
            {
                TIFFReadEncodedStrip( hTIFF,
                                      TIFFComputeStrip(hTIFF, nSYOff,
                                                       (tsample_t) iSample),
                                      pabySrcTile,
                                      TIFFStripSize(hTIFF) );
            }
        }

        /*        
         * Loop over destination overview layers
         */
        for( iOverview = 0; iOverview < nOverviews; iOverview++ )
        {
            TIFFOvrCache *poRBI = papoRawBIs[iOverview];
            unsigned char *pabyOTile;
            int	nTXOff, nTYOff, nOXOff, nOYOff, nOMult;
            int	nOBlockXSize = poRBI->nBlockXSize;
            int	nOBlockYSize = poRBI->nBlockYSize;
            int	nSkewBits, nSampleByteOffset; 

            /*
             * Fetch the destination overview tile
             */
            nOMult = panOvList[iOverview];
            nOXOff = (nSXOff/nOMult) / nOBlockXSize;
            nOYOff = (nSYOff/nOMult) / nOBlockYSize;
            pabyOTile = TIFFGetOvrBlock( poRBI, nOXOff, nOYOff, iSample );
                
            /*
             * Establish the offset into this tile at which we should
             * start placing data.
             */
            nTXOff = (nSXOff - nOXOff*nOMult*nOBlockXSize) / nOMult;
            nTYOff = (nSYOff - nOYOff*nOMult*nOBlockYSize) / nOMult;

            /*
             * Figure out the skew (extra space between ``our samples'') and
             * the byte offset to the first sample.
             */
            assert( (nBitsPerPixel % 8) == 0 );
            if( nPlanarConfig == PLANARCONFIG_SEPARATE )
            {
                nSkewBits = 0;
                nSampleByteOffset = 0;
            }
            else
            {
                nSkewBits = nBitsPerPixel * (nSamples-1);
                nSampleByteOffset = (nBitsPerPixel/8) * iSample;
            }
            
            /*
             * Perform the downsampling.
             */
#ifdef DBMALLOC
            malloc_chain_check( 1 );
#endif
            TIFF_DownSample( pabySrcTile + nSampleByteOffset,
                             nBlockXSize, nBlockYSize,
                             nSkewBits, nBitsPerPixel, pabyOTile,
                             poRBI->nBlockXSize, poRBI->nBlockYSize,
                             nTXOff, nTYOff,
                             nOMult, nSampleFormat, pszResampling );
#ifdef DBMALLOC
            malloc_chain_check( 1 );
#endif            
        }
    }
}

/************************************************************************/
/*                        TIFF_BuildOverviews()                         */
/*                                                                      */
/*      Build the requested list of overviews.  Overviews are           */
/*      maintained in a bunch of temporary files and then these are     */
/*      written back to the TIFF file.  Only one pass through the       */
/*      source TIFF file is made for any number of output               */
/*      overviews.                                                      */
/************************************************************************/

void TIFFBuildOverviews( TIFF *hTIFF, int nOverviews, int * panOvList,
                         int bUseSubIFDs, const char *pszResampleMethod,
                         int (*pfnProgress)( double, void * ),
                         void * pProgressData )

{
    TIFFOvrCache	**papoRawBIs;
    uint32		nXSize, nYSize, nBlockXSize, nBlockYSize;
    uint16		nBitsPerPixel, nPhotometric, nCompressFlag, nSamples,
                        nPlanarConfig, nSampleFormat;
    int			bTiled, nSXOff, nSYOff, i;
    unsigned char	*pabySrcTile;
    uint16		*panRedMap, *panGreenMap, *panBlueMap;
    TIFFErrorHandler    pfnWarning;

/* -------------------------------------------------------------------- */
/*      Get the base raster size.                                       */
/* -------------------------------------------------------------------- */
    TIFFGetField( hTIFF, TIFFTAG_IMAGEWIDTH, &nXSize );
    TIFFGetField( hTIFF, TIFFTAG_IMAGELENGTH, &nYSize );

    TIFFGetField( hTIFF, TIFFTAG_BITSPERSAMPLE, &nBitsPerPixel );
    TIFFGetField( hTIFF, TIFFTAG_SAMPLESPERPIXEL, &nSamples );
    TIFFGetFieldDefaulted( hTIFF, TIFFTAG_PLANARCONFIG, &nPlanarConfig );

    TIFFGetFieldDefaulted( hTIFF, TIFFTAG_PHOTOMETRIC, &nPhotometric );
    TIFFGetFieldDefaulted( hTIFF, TIFFTAG_COMPRESSION, &nCompressFlag );
    TIFFGetFieldDefaulted( hTIFF, TIFFTAG_SAMPLEFORMAT, &nSampleFormat );

    if( nBitsPerPixel < 8 )
    {
        TIFFError( "TIFFBuildOverviews",
                   "File `%s' has samples of %d bits per sample.  Sample\n"
                   "sizes of less than 8 bits per sample are not supported.\n",
                   TIFFFileName(hTIFF), nBitsPerPixel );
        return;
    }
    
/* -------------------------------------------------------------------- */
/*      Turn off warnings to avoid alot of repeated warnings while      */
/*      rereading directories.                                          */
/* -------------------------------------------------------------------- */
    pfnWarning = TIFFSetWarningHandler( NULL );

/* -------------------------------------------------------------------- */
/*      Get the base raster block size.                                 */
/* -------------------------------------------------------------------- */
    if( TIFFGetField( hTIFF, TIFFTAG_ROWSPERSTRIP, &(nBlockYSize) ) )
    {
        nBlockXSize = nXSize;
        bTiled = FALSE;
    }
    else
    {
        TIFFGetField( hTIFF, TIFFTAG_TILEWIDTH, &nBlockXSize );
        TIFFGetField( hTIFF, TIFFTAG_TILELENGTH, &nBlockYSize );
        bTiled = TRUE;
    }

/* -------------------------------------------------------------------- */
/*	Capture the pallette if there is one.				*/
/* -------------------------------------------------------------------- */
    if( TIFFGetField( hTIFF, TIFFTAG_COLORMAP,
                      &panRedMap, &panGreenMap, &panBlueMap ) )
    {
        uint16		*panRed2, *panGreen2, *panBlue2;
        int             nColorCount = 1 << nBitsPerPixel;

        panRed2 = (uint16 *) _TIFFmalloc(2*nColorCount);
        panGreen2 = (uint16 *) _TIFFmalloc(2*nColorCount);
        panBlue2 = (uint16 *) _TIFFmalloc(2*nColorCount);

        memcpy( panRed2, panRedMap, 2 * nColorCount );
        memcpy( panGreen2, panGreenMap, 2 * nColorCount );
        memcpy( panBlue2, panBlueMap, 2 * nColorCount );

        panRedMap = panRed2;
        panGreenMap = panGreen2;
        panBlueMap = panBlue2;
    }
    else
    {
        panRedMap = panGreenMap = panBlueMap = NULL;
    }
        
/* -------------------------------------------------------------------- */
/*      Initialize overviews.                                           */
/* -------------------------------------------------------------------- */
    papoRawBIs = (TIFFOvrCache **) _TIFFmalloc(nOverviews*sizeof(void*));

    for( i = 0; i < nOverviews; i++ )
    {
        int	nOXSize, nOYSize, nOBlockXSize, nOBlockYSize;
        uint32  nDirOffset;

        nOXSize = (nXSize + panOvList[i] - 1) / panOvList[i];
        nOYSize = (nYSize + panOvList[i] - 1) / panOvList[i];

        nOBlockXSize = MIN((int)nBlockXSize,nOXSize);
        nOBlockYSize = MIN((int)nBlockYSize,nOYSize);

        if( bTiled )
        {
            if( (nOBlockXSize % 16) != 0 )
                nOBlockXSize = nOBlockXSize + 16 - (nOBlockXSize % 16);
            
            if( (nOBlockYSize % 16) != 0 )
                nOBlockYSize = nOBlockYSize + 16 - (nOBlockYSize % 16);
        }

        nDirOffset = TIFF_WriteOverview( hTIFF, nOXSize, nOYSize,
                                         nBitsPerPixel, nPlanarConfig,
                                         nSamples, nOBlockXSize, nOBlockYSize,
                                         bTiled, nCompressFlag, nPhotometric,
                                         nSampleFormat,
                                         panRedMap, panGreenMap, panBlueMap,
                                         bUseSubIFDs );
        
        papoRawBIs[i] = TIFFCreateOvrCache( hTIFF, nDirOffset );
    }

    if( panRedMap != NULL )
    {
        _TIFFfree( panRedMap );
        _TIFFfree( panGreenMap );
        _TIFFfree( panBlueMap );
    }
    
/* -------------------------------------------------------------------- */
/*      Allocate a buffer to hold a source block.                       */
/* -------------------------------------------------------------------- */
    if( bTiled )
        pabySrcTile = (unsigned char *) _TIFFmalloc(TIFFTileSize(hTIFF));
    else
        pabySrcTile = (unsigned char *) _TIFFmalloc(TIFFStripSize(hTIFF));
    
/* -------------------------------------------------------------------- */
/*      Loop over the source raster, applying data to the               */
/*      destination raster.                                             */
/* -------------------------------------------------------------------- */
    for( nSYOff = 0; nSYOff < (int) nYSize; nSYOff += nBlockYSize )
    {
        for( nSXOff = 0; nSXOff < (int) nXSize; nSXOff += nBlockXSize )
        {
            /*
             * Read and resample into the various overview images.
             */
            
            TIFF_ProcessFullResBlock( hTIFF, nPlanarConfig,
                                      nOverviews, panOvList,
                                      nBitsPerPixel, nSamples, papoRawBIs,
                                      nSXOff, nSYOff, pabySrcTile,
                                      nBlockXSize, nBlockYSize,
                                      nSampleFormat, pszResampleMethod );
        }
    }

    _TIFFfree( pabySrcTile );

/* -------------------------------------------------------------------- */
/*      Cleanup the rawblockedimage files.                              */
/* -------------------------------------------------------------------- */
    for( i = 0; i < nOverviews; i++ )
    {
        TIFFDestroyOvrCache( papoRawBIs[i] );
    }

    if( papoRawBIs != NULL )
        _TIFFfree( papoRawBIs );

    TIFFSetWarningHandler( pfnWarning );
}