[gdal-dev] Fwd: Re: [Tiff] Libtiff will be released soon

[Even Rouault]

On lundi 12 novembre 2018 08:48:59 CET Robert Coup wrote:
> Hi Even,
> 
> On Mon, 12 Nov 2018 at 07:57, Even Rouault <even.rouault at spatialys.com>
> 
> wrote:
> > Not completely sure what to do with GDAL 2.3 branch, as it already had
> > ZStd
> > (if using its internal libtiff copy). I feel it is probably wise to also
> > update the modified value of COMPRESSION_ZSTD there to avoid the risk of
> > people creating files with the now obsolete tag value ?
> 
> How about:
> 
> 1. Read both values as enabling ZSTD
> 2. Output a warning when the old value is encountered
> 3. Always write the new value

Yeah, that's just what I have done. But only in 2.3 branch, not in master, as 
I patched the internal libtiff copy for that, and don't intend to upstream 
that hack or make the internal libtiff in master diverge from official 
libtiff.

$ gdalinfo ../autotest/gcore/data/byte_zstd.tif
Warning 1: TIFFInitZSTD:Value of Compression Tag is 34926, which is the 
deprecated value for ZStd. Please use the new value of 50000 by recreating/
patching this file. Next GDAL releases won't recognize this file.
Driver: GTiff/GeoTIFF
Files: ../autotest/gcore/data/byte_zstd.tif
[...]

Note: if you build GDAL 2.3 with the shiny new libtiff 4.0.10 as external 
libtiff, those files with 34926 won't be recognized.

Even


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