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2017.08.26 13:56 "Determining use of "w" or "w8" in TIFFOpen", by Paul Hemmer
2017.08.26 14:19 "Re: Determining use of "w" or "w8" in TIFFOpen", by <jcupitt@gmail.com>
2017.08.26 14:54 "Re: Determining use of "w" or "w8" in TIFFOpen", by Paul Hemmer
2017.08.26 15:14 "Re: Determining use of "w" or "w8" in TIFFOpen", by Paavo Helde
2017.08.26 15:22 "Re: Determining use of "w" or "w8" in TIFFOpen", by Paul Hemmer
2017.08.26 15:31 "Re: Determining use of "w" or "w8" in TIFFOpen", by Paul Hemmer
2017.08.26 17:44 "Re: Determining use of "w" or "w8" in TIFFOpen", by Paavo Helde
2017.08.26 15:23 "Re: Determining use of "w" or "w8" in TIFFOpen", by <jcupitt@gmail.com>
2017.08.26 15:31 "Re: Determining use of "w" or "w8" in TIFFOpen", by Roger Leigh
2017.08.26 15:38 "Re: Determining use of "w" or "w8" in TIFFOpen", by Paul Hemmer

2017.08.26 14:54 "Re: Determining use of "w" or "w8" in TIFFOpen", by Paul Hemmer

Thank you John for your reply.


I see, I wasn't aware that only certain programs support BigTIFF.


That being said, if my [height*width*2] calculation results in a value
greater than 4GB and I specify "wb" as the open option, but the LZW
compressed data ends up taking less than 4GB, the resulting file will still
be a "BigTIFF File" and should be viewable inside an image viewer that does
support BigTIFF?


ie. can BigTIFF be used for files that are smaller than 4GB due to the
compression?


Thanks!



-Paul



________________________________
From: jcupitt@gmail.com <jcupitt@gmail.com>
Sent: Saturday, August 26, 2017 10:19 AM
To: Paul Hemmer
Cc: tiff@lists.maptools.org
Subject: Re: [Tiff] Determining use of "w" or "w8" in TIFFOpen

Hello Paul,

On 26 August 2017 at 14:56, Paul Hemmer <paulhemmer@hotmail.com> wrote:
> If that size is greater than 4GB, I should specify "w8" and if less than,
> I
> should specify "w" when calling TIFFOpen() in order to get the BigTIFF
> format when needed.
>
> But what if the use of COMPRESSION_LZW would result in a file that is much
> smaller than 4GB? I can't know that ahead of time (can I?)  Should I still
> use w8 if the uncompressed dimensions require more than 4GB?

I handle this by enabling bigtiff mode automatically if I'm writing an
uncompressed TIFF which will be over 4GB. If compression is turned on,
users have to tick a box (or pass an option) to enable bigtiff write.
It's a bit unsatisfactory.

> I'm finding that I can't simply specify "w8" for all, as those that are
> less
> than 4GB end up failing to open.

They should only fail to open if the program you are using does not
support bigtiff.

Sadly, rather few programs support bigtiff, hence the need to have it
as an option that users must explicitly turn on.

John