[gdal-dev] Updating value for Compression tag for JPEGXL in TIFF to the one of DNG 1.7 ?

[Even Rouault]

Hi,

Given that communication with Adobe in recent years has been similar to 
expecting to receive a signal from a black hole from outside its event 
horizon, up to now we have unilaterally attributed Compression=50002 to 
mean JPEGXL in TIFF. Recently I saw that the DNG 1.7 specification has 
registered value 52546 to mean JPEGXL in DNG 
(https://helpx.adobe.com/content/dam/help/en/photoshop/pdf/DNG_Spec_1_7_0_0.pdf 
, page 122). DNG is a derivative of the TIFF spec, so I guess/hope Adobe 
makes sure that tag & tag value numbers don't collide between base TIFF 
and DNG. So it would seem to me that switching to using the 52546 value 
would be more future proof than our self-assigned 50002. If so, I'd do 
the change in master to using 52546 on write side and accepting both 
50002 and 52546 on read side, and backport read support for 52546 in 3.10

(this is mostly a GDAL-only topic for now given that the JPEGXL TIFF 
codec is for the internal libtiff copy only)

Thoughts?

Even

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