tif_read.c

一个国人自己实现图像库的程序（有参考价值）

 */

/*
 * Read and decompress a tile of data.  The
 * tile is selected by the (x,y,z,s) coordinates.
 */
tsize_t
TIFFReadTile(TIFF* tif,
    tdata_t buf, uint32 x, uint32 y, uint32 z, tsample_t s)
{
	if (!TIFFCheckRead(tif, 1) || !TIFFCheckTile(tif, x, y, z, s))
		return (-1);
	return (TIFFReadEncodedTile(tif,
	    TIFFComputeTile(tif, x, y, z, s), buf, (tsize_t) -1));
}

/*
 * Read a tile of data and decompress the specified
 * amount into the user-supplied buffer.
 */
tsize_t
TIFFReadEncodedTile(TIFF* tif, ttile_t tile, tdata_t buf, tsize_t size)
{
	TIFFDirectory *td = &tif->tif_dir;
	tsize_t tilesize = tif->tif_tilesize;

	if (!TIFFCheckRead(tif, 1))
		return (-1);
	if (tile >= td->td_nstrips) {
		TIFFError(tif->tif_name, "%ld: Tile out of range, max %ld",
		    (long) tile, (u_long) td->td_nstrips);
		return (-1);
	}
	if (size == (tsize_t) -1)
		size = tilesize;
	else if (size > tilesize)
		size = tilesize;
	if (TIFFFillTile(tif, tile) && (*tif->tif_decodetile)(tif,
	    (tidata_t) buf, size, (tsample_t)(tile/td->td_stripsperimage))) {
		(*tif->tif_postdecode)(tif, (tidata_t) buf, size);
		return (size);
	} else
		return (-1);
}

static tsize_t
TIFFReadRawTile1(TIFF* tif,
    ttile_t tile, tdata_t buf, tsize_t size, const char* module)
{
	TIFFDirectory *td = &tif->tif_dir;

	if (!isMapped(tif)) {
		tsize_t cc;

		if (!SeekOK(tif, td->td_stripoffset[tile])) {
			TIFFError(module,
			    "%s: Seek error at row %ld, col %ld, tile %ld",
			    tif->tif_name,
			    (long) tif->tif_row,
			    (long) tif->tif_col,
			    (long) tile);
			return ((tsize_t) -1);
		}
		cc = TIFFReadFile(tif, buf, size);
		if (cc != size) {
			TIFFError(module,
	    "%s: Read error at row %ld, col %ld; got %lu bytes, expected %lu",
			    tif->tif_name,
			    (long) tif->tif_row,
			    (long) tif->tif_col,
			    (u_long) cc,
			    (u_long) size);
			return ((tsize_t) -1);
		}
	} else {
		if (td->td_stripoffset[tile] + size > tif->tif_size) {
			TIFFError(module,
    "%s: Read error at row %ld, col %ld, tile %ld; got %lu bytes, expected %lu",
			    tif->tif_name,
			    (long) tif->tif_row,
			    (long) tif->tif_col,
			    (long) tile,
			    (u_long) tif->tif_size - td->td_stripoffset[tile],
			    (u_long) size);
			return ((tsize_t) -1);
		}
		_TIFFmemcpy(buf, tif->tif_base + td->td_stripoffset[tile], size);
	}
	return (size);
}

/*
 * Read a tile of data from the file.
 */
tsize_t
TIFFReadRawTile(TIFF* tif, ttile_t tile, tdata_t buf, tsize_t size)
{
	static const char module[] = "TIFFReadRawTile";
	TIFFDirectory *td = &tif->tif_dir;
	tsize_t bytecount;

	if (!TIFFCheckRead(tif, 1))
		return ((tsize_t) -1);
	if (tile >= td->td_nstrips) {
		TIFFError(tif->tif_name, "%lu: Tile out of range, max %lu",
		    (u_long) tile, (u_long) td->td_nstrips);
		return ((tsize_t) -1);
	}
	bytecount = td->td_stripbytecount[tile];
	if (size != (tsize_t) -1 && size < bytecount)
		bytecount = size;
	return (TIFFReadRawTile1(tif, tile, buf, bytecount, module));
}

/*
 * Read the specified tile and setup for decoding. 
 * The data buffer is expanded, as necessary, to
 * hold the tile's data.
 */
static int
TIFFFillTile(TIFF* tif, ttile_t tile)
{
	static const char module[] = "TIFFFillTile";
	TIFFDirectory *td = &tif->tif_dir;
	tsize_t bytecount;

	bytecount = td->td_stripbytecount[tile];
	if (bytecount <= 0) {
		TIFFError(tif->tif_name,
		    "%lu: Invalid tile byte count, tile %lu",
		    (u_long) bytecount, (u_long) tile);
		return (0);
	}
	if (isMapped(tif) &&
	    (isFillOrder(tif, td->td_fillorder) || (tif->tif_flags & TIFF_NOBITREV))) {
		/*
		 * The image is mapped into memory and we either don't
		 * need to flip bits or the compression routine is going
		 * to handle this operation itself.  In this case, avoid
		 * copying the raw data and instead just reference the
		 * data from the memory mapped file image.  This assumes
		 * that the decompression routines do not modify the
		 * contents of the raw data buffer (if they try to,
		 * the application will get a fault since the file is
		 * mapped read-only).
		 */
		if ((tif->tif_flags & TIFF_MYBUFFER) && tif->tif_rawdata)
			_TIFFfree(tif->tif_rawdata);
		tif->tif_flags &= ~TIFF_MYBUFFER;
		if ( td->td_stripoffset[tile] + bytecount > tif->tif_size) {
			tif->tif_curtile = NOTILE;
			return (0);
		}
		tif->tif_rawdatasize = bytecount;
		tif->tif_rawdata = tif->tif_base + td->td_stripoffset[tile];
	} else {
		/*
		 * Expand raw data buffer, if needed, to
		 * hold data tile coming from file
		 * (perhaps should set upper bound on
		 *  the size of a buffer we'll use?).
		 */
		if (bytecount > tif->tif_rawdatasize) {
			tif->tif_curtile = NOTILE;
			if ((tif->tif_flags & TIFF_MYBUFFER) == 0) {
				TIFFError(module,
				"%s: Data buffer too small to hold tile %ld",
				    tif->tif_name, (long) tile);
				return (0);
			}
			if (!TIFFReadBufferSetup(tif, 0,
			    TIFFroundup(bytecount, 1024)))
				return (0);
		}
		if (TIFFReadRawTile1(tif, tile, (u_char *)tif->tif_rawdata,
		    bytecount, module) != bytecount)
			return (0);
		if (!isFillOrder(tif, td->td_fillorder) &&
		    (tif->tif_flags & TIFF_NOBITREV) == 0)
			TIFFReverseBits(tif->tif_rawdata, bytecount);
	}
	return (TIFFStartTile(tif, tile));
}

/*
 * Setup the raw data buffer in preparation for
 * reading a strip of raw data.  If the buffer
 * is specified as zero, then a buffer of appropriate
 * size is allocated by the library.  Otherwise,
 * the client must guarantee that the buffer is
 * large enough to hold any individual strip of
 * raw data.
 */
int
TIFFReadBufferSetup(TIFF* tif, tdata_t bp, tsize_t size)
{
	static const char module[] = "TIFFReadBufferSetup";

	if (tif->tif_rawdata) {
		if (tif->tif_flags & TIFF_MYBUFFER)
			_TIFFfree(tif->tif_rawdata);
		tif->tif_rawdata = NULL;
	}
	if (bp) {
		tif->tif_rawdatasize = size;
		tif->tif_rawdata = (tidata_t) bp;
		tif->tif_flags &= ~TIFF_MYBUFFER;
	} else {
		tif->tif_rawdatasize = TIFFroundup(size, 1024);
		tif->tif_rawdata = (tidata_t) _TIFFmalloc(tif->tif_rawdatasize);
		tif->tif_flags |= TIFF_MYBUFFER;
	}
	if (tif->tif_rawdata == NULL) {
		TIFFError(module,
		    "%s: No space for data buffer at scanline %ld",
		    tif->tif_name, (long) tif->tif_row);
		tif->tif_rawdatasize = 0;
		return (0);
	}
	return (1);
}

/*
 * Set state to appear as if a
 * strip has just been read in.
 */
static int
TIFFStartStrip(TIFF* tif, tstrip_t strip)
{
	TIFFDirectory *td = &tif->tif_dir;

	if ((tif->tif_flags & TIFF_CODERSETUP) == 0) {
		if (!(*tif->tif_setupdecode)(tif))
			return (0);
		tif->tif_flags |= TIFF_CODERSETUP;
	}
	tif->tif_curstrip = strip;
	tif->tif_row = (strip % td->td_stripsperimage) * td->td_rowsperstrip;
	tif->tif_rawcp = tif->tif_rawdata;
	tif->tif_rawcc = td->td_stripbytecount[strip];
	return ((*tif->tif_predecode)(tif,
			(tsample_t)(strip / td->td_stripsperimage)));
}

/*
 * Set state to appear as if a
 * tile has just been read in.
 */
static int
TIFFStartTile(TIFF* tif, ttile_t tile)
{
	TIFFDirectory *td = &tif->tif_dir;

	if ((tif->tif_flags & TIFF_CODERSETUP) == 0) {
		if (!(*tif->tif_setupdecode)(tif))
			return (0);
		tif->tif_flags |= TIFF_CODERSETUP;
	}
	tif->tif_curtile = tile;
	tif->tif_row =
	    (tile % TIFFhowmany(td->td_imagewidth, td->td_tilewidth)) *
		td->td_tilelength;
	tif->tif_col =
	    (tile % TIFFhowmany(td->td_imagelength, td->td_tilelength)) *
		td->td_tilewidth;
	tif->tif_rawcp = tif->tif_rawdata;
	tif->tif_rawcc = td->td_stripbytecount[tile];
	return ((*tif->tif_predecode)(tif,
			(tsample_t)(tile/td->td_stripsperimage)));
}

static int
TIFFCheckRead(TIFF* tif, int tiles)
{
	if (tif->tif_mode == O_WRONLY) {
		TIFFError(tif->tif_name, "File not open for reading");
		return (0);
	}
	if (tiles ^ isTiled(tif)) {
		TIFFError(tif->tif_name, tiles ?
		    "Can not read tiles from a stripped image" :
		    "Can not read scanlines from a tiled image");
		return (0);
	}
	return (1);
}

void
_TIFFNoPostDecode(TIFF* tif, tidata_t buf, tsize_t cc)
{
    (void) tif; (void) buf; (void) cc;
}

void
_TIFFSwab16BitData(TIFF* tif, tidata_t buf, tsize_t cc)
{
    (void) tif;
    assert((cc & 1) == 0);
    TIFFSwabArrayOfShort((uint16*) buf, cc/2);
}

void
_TIFFSwab32BitData(TIFF* tif, tidata_t buf, tsize_t cc)
{
    (void) tif;
    assert((cc & 3) == 0);
    TIFFSwabArrayOfLong((uint32*) buf, cc/4);
}

void
_TIFFSwab64BitData(TIFF* tif, tidata_t buf, tsize_t cc)
{
    (void) tif;
    assert((cc & 7) == 0);
    TIFFSwabArrayOfDouble((double*) buf, cc/8);
}