LibTiff Mailing List

xevit wrote:

> My problem is that when I'm working on a big TIFF file ( tile 
> based ) I want to read and write simultaneous to the same file,
> to change small portions of my bigImage.

I have never tried it, but I guess it should be possible to open the TIFF as
a normal file (using open() on Unix or CreateFile() on Win32; see the code
in tif_unix.c, tif_win32.c, or the appropriate file for your OS), and then
pass the returned file descriptor to TIFFFdOpen(). Then you can use libtiff
to read the strip offsets and sizes, and use the normal file handle to
lseek() (or SetFilePointer() or whatever) to the correct offset within the
file and overwrite the data there. I'm not sure whether it would be wise to
use any of libtiff's write functions.

Of course, this will all only work when the TIFF is uncompressed! Otherwise,
the (compressed) size of the data could change, and all bets are off.

It would be interesting to hear from anyone who has ever tried this kind of
thing with libtiff.

					Gerben Vos.


AWARE [SYSTEMS]		Imaging expertise for the Delphi developer
		TIFF and LibTiff Mailing List Archive
	LibTiff Mailing List TIFF and LibTiff Mailing List Archive March 2004 Previous Thread Next Thread Previous by Thread Next by Thread Previous by Date Next by Date Contact The TIFF Mailing List Homepage This list is run by Frank Warmerdam Archive maintained by AWare Systems	Thread 2004.03.01 20:10 "Hello world", by <xevit@isildur.homelinux.net> 2004.03.01 22:10 "Re: Hello world", by Chris Cox 2004.03.02 23:14 "Re: Hello world", by <xevit@isildur.homelinux.net> 2004.03.02 23:16 "Re: Hello world", by Pushkar Pradhan 2004.03.03 11:16 "Re: Hello world", by Gerben Vos 2004.03.03 12:02 "Re: Hello world", by Rob Tillaart 2004.03.03 14:18 "Re: Hello world", by Frank Warmerdam 2004.03.03 11:16 "Re: Hello world", by Gerben Vos xevit wrote: > My problem is that when I'm working on a big TIFF file ( tile > based ) I want to read and write simultaneous to the same file, > to change small portions of my bigImage. I have never tried it, but I guess it should be possible to open the TIFF as a normal file (using open() on Unix or CreateFile() on Win32; see the code in tif_unix.c, tif_win32.c, or the appropriate file for your OS), and then pass the returned file descriptor to TIFFFdOpen(). Then you can use libtiff to read the strip offsets and sizes, and use the normal file handle to lseek() (or SetFilePointer() or whatever) to the correct offset within the file and overwrite the data there. I'm not sure whether it would be wise to use any of libtiff's write functions. Of course, this will all only work when the TIFF is uncompressed! Otherwise, the (compressed) size of the data could change, and all bets are off. It would be interesting to hear from anyone who has ever tried this kind of thing with libtiff. Gerben Vos.

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2004.03.03 11:16 "Re: Hello world", by Gerben Vos