LibTiff Mailing List

xevit wrote:
> Hello everybody.
> 
> I'm working on a vision project, and I want to make a viewer for a large 
> files ( >= 4Gb ).
> Currently I've developed a small viewer using libtiff that works on a 
> tiled image that makes 100.000 x 100.000, and works fine.
> Altrought, I have some problems because I want to read and write some 
> tiles in this file without doing the read from one file, and writing to 
> another.
> 
> I've been read some information about this, and I find that libtiff 
> don't support this. Anybody knows a solution for this problem or 
> alternative.
> Thank's in advance.
> 
> P.D Sorry for my English.

Xevit,

I'm not sure how you are addressing the > 4GB issue.

There has been some work to implement support for random update of
TIFF files with libtiff.  Open it the mode string "r+" to TIFFOpen() and
you can (with many restrictions) read and write the file.

Generally this works best for uncompressed files, but I *think* it can work
for compressed files as well with the caveat that if you write a block with
a larger compressed representation than the old one, it will be added at the
end of the file, and the old strip/tile space will be lost.

This is a relatively recent innovation in libtiff, and is undoubtedly buggy
in many regards but it does allow "in place" update of TIFF files in some
sitations.

Try opening the file with mode="r+" and then report (via small example
programs) what goes wrong.

Best regards,
-- 
---------------------------------------+--------------------------------------
I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam@pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | Geospatial Programmer for Rent


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 14:18 "Re: Hello world", by Frank Warmerdam xevit wrote: > Hello everybody. > > I'm working on a vision project, and I want to make a viewer for a large > files ( >= 4Gb ). > Currently I've developed a small viewer using libtiff that works on a > tiled image that makes 100.000 x 100.000, and works fine. > Altrought, I have some problems because I want to read and write some > tiles in this file without doing the read from one file, and writing to > another. > > I've been read some information about this, and I find that libtiff > don't support this. Anybody knows a solution for this problem or > alternative. > Thank's in advance. > > P.D Sorry for my English. Xevit, I'm not sure how you are addressing the > 4GB issue. There has been some work to implement support for random update of TIFF files with libtiff. Open it the mode string "r+" to TIFFOpen() and you can (with many restrictions) read and write the file. Generally this works best for uncompressed files, but I think it can work for compressed files as well with the caveat that if you write a block with a larger compressed representation than the old one, it will be added at the end of the file, and the old strip/tile space will be lost. This is a relatively recent innovation in libtiff, and is undoubtedly buggy in many regards but it does allow "in place" update of TIFF files in some sitations. Try opening the file with mode="r+" and then report (via small example programs) what goes wrong. Best regards, -- ---------------------------------------+-------------------------------------- I set the clouds in motion - turn up \| Frank Warmerdam, warmerdam@pobox.com light and sound - activate the windows \| http://pobox.com/~warmerdam and watch the world go round - Rush \| Geospatial Programmer for Rent

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2004.03.03 14:18 "Re: Hello world", by Frank Warmerdam