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2018.12.12 22:21 "Fwd: TIFFSetDirectory and TIFFCurrentDirectory issues in libtif 4.0.10", by Bardas Georgios
2018.12.12 22:57 "Re: Fwd: TIFFSetDirectory and TIFFCurrentDirectory issues in libtif 4.0.10", by Kemp Watson
2018.12.13 15:00 "Re: Fwd: TIFFSetDirectory and TIFFCurrentDirectory issues in libtif 4.0.10", by Olivier Paquet

2018.12.12 22:57 "Re: Fwd: TIFFSetDirectory and TIFFCurrentDirectory issues in libtif 4.0.10", by Kemp Watson

Hi George:

If this is pathology with whole slide images, drop me a line, I might be
able to save you a lot of time you could put on other aspects of your
project, or also check out the OpenSlide project or BioFormats.

If by “so big” you mean more than 4GB or 65K pixels on a side, you will be
looking at BigTIFF, not TIFF.

Else, yes, you can go back and read a previous directory, but I don’t
believe you can go back to write it (add to I mean, you can start again with
TIFFRewriteDirectory()) – anyway, you still probably have access to your
source data, just don’t close those files/blobs until the decimated tiles
are written – that way, you’ll have at most ¼ of your image in memory at any
time, even with a naïve approach, and you won’t need to re-read anything at
all.

Also, I might make mention that almost everyone does reduced-resolution
images totally incorrectly according to the spec – they should be in
SubIFDs, not IFDs, to be properly compliant with the intent of the TIFF
specification regarding alternate renditions of the same data.

Kemp Watson

From: Tiff <tiff-bounces@lists.osgeo.org> on behalf of Bardas Georgios
<geobar2010@gmail.com>
Date: Wednesday, December 12, 2018 at 5:21 PM
To: "tiff@lists.osgeo.org" <tiff@lists.osgeo.org>
Subject: [Tiff] Fwd: TIFFSetDirectory and TIFFCurrentDirectory issues in
libtif 4.0.10

Hello gentlemen,
I have been working in Libtiff for one or two weeks now, and i am stuck into
some mysterious problem. I am using libtiff 4.0.10 in Visual Studio 2017 and
just trying to do the following task: I am willing to fill the first page
(directory) with some data (black tiles (256x256) for example) and then i
need to read that information and write it on the next page decimated by
two. In fact all i am trying to make is a tiled pyramid tiff image which the
level 0 is so big i can parse it only through tiles. My question is: Is it
possible to write one directory and then return back and read from it to
write that data on the next directory?

Currenlty i am using TIFFSetDirectory to try and get back to the previous
one, but unfortunately it fails (TIFFSetDirectory(tiff,0) returns 0) after i
have saved the previous' directory's data with TIFFWriteDirectory.

On the other hand, when i use TIFFCurrentDirectory on the first directory i
write, strangely i get "65536" instead of 0 (probably -1 in uint), why? And
when i write this folder it goes to folder 0, then 1 etc. To sum up
TIFFCurrentDirectory seems to return n-1, where n is the current directory's
number.

Can anyone help me?
Thanks a lot,
George.


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