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February 2005

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2005.02.28 11:51 "Delphi TIFF visualization", by José Núñez
2005.02.28 12:41 "Re: Delphi TIFF visualization", by Joris Van Damme
2005.02.28 12:48 "Re: Delphi TIFF visualization", by Joris Van Damme
2005.02.28 12:58 "Re: Delphi TIFF visualization", by José Núñez
2005.02.28 13:16 "Re: Delphi TIFF visualization", by José Núñez
2005.02.28 13:44 "Re: Delphi TIFF visualization", by Joris Van Damme
2005.02.28 13:27 "Re: Delphi TIFF visualization", by Joris Van Damme

2005.02.28 13:44 "Re: Delphi TIFF visualization", by Joris Van Damme

José,

> Sorry, your other mail was marked by my mail server as Spam. I have
> copy-pasted what you send and tested it. It works fine with some "easy"
> files, but I obtain a blank image with my "preffered" one. Those are my
> tags:
> ...
> Compression (1 Short): JPEG Original TIFF 6.0 spec
> ...
> Do you detect something not compatible with TIFF specifications?

The problem here is the compression mode. You should contact the vendor of the
software that generated the TIFF. The TIFF community has long condemned and
abandonded this original 6.0 jpeg-in-tiff compression scheme, because the
original specification was ambiguous and plainly breaking TIFF. Tom Lane has
written a replacement many many years ago, Technote2,
http://www.remotesensing.org/libtiff/TIFFTechNote2.html, and Adobe have absorbed
that replacement in a specification supplement
http://partners.adobe.com/public/developer/en/tiff/TIFFphotoshop.pdf.
Nevertheless, vendors who prefer monopoly at the cost of portability of data
insist on writing their particular interpretation of original jpeg-in-tiff
compression because we obviously haven't complained enough yet.

LibTiff does try to support reading some vendors' particular interpretations of
original 6.0 jpeg-in-tiff. However, it cannot claim to be perfect and complete,
the original specification was ambiguous. It quite correctly does not support
writing original 6.0 jpeg-in-tiff. LibTiffDelphi 3.7.0.00 does *not* support
reading this compression scheme. (The reason is technical, despite my additional
theoretical objections. Avoiding C runtimes and all such additional weight, I
cannot make use of longjumps or exceptions in C. This means that I cannot
directly make use of LibJpeg in LibTiffDelphi. Thus, I have to make a detour,
LibTiffDelphi calls wrappers of LibJpeg functions in pascal instead, where I can
make use of exception handling for trapping and handling LibJpeg errors. This is
a lot of additional hassle. I've put in the work for the good Technote2
jpeg-in-tiff compression scheme, but have not yet done so for abandoned old 6.0
jpeg-in-tiff.)

I am however considering investing the work it takes to include LibTiff's normal
old-style 6.0 jpeg-in-tiff reading support. If I do, I will do so when I upgrade
the package to LibTiff 3.7.1, probably some time soon. I will at that time also
remove the 'beta' status, and start adding proper documentation. If you want to
be kept informed when this happens, I recommend using the appropriate 'drop us a
line' mail-link on the LibTiffDelphi download page
http://www.awaresystems.be/imaging/tiff/delphi.html.

Sorry for the inconvinience.


Joris Van Damme
info@awaresystems.be
http://www.awaresystems.be/
Download your free TIFF tag viewer for windows here:
http://www.awaresystems.be/imaging/tiff/astifftagviewer.html