[gdal-dev] How to generate COG without loosing Exif, XMP etc metadata

[Even Rouault]

Luigi,

The GDAL GeoTIFF or COG drivers have currently no provision for writing 
EXIF (the fact that you see Exif.Image.Software is due to, I assume, 
exiftool synthetizing that information from the regular Software TIFF 
tag, which is propagated), so I don't have any solution to offer. Could 
potentially be implemented, but not a 5-minute job.

"Breaking" the COG structure shouldn't be the end of the world. The 
breakage should be minimal. That will just cause one extra HTTP GET to 
clients. 95% of the value of COG is just being a tiled GeoTIFF with 
overviews. Putting all metadata (including the main TIFF directory) at 
beginning of the file is just the cherry on the cake.

(a quick skim at https://github.com/airbusgeo/cogger which is useful to 
COGify a tiled GeoTIFF doesn't show any provision for EXIF, so I don't 
think you can use it for your use case)

The XMP TIFF tag is propagated:

$ gdal_translate autotest/gdrivers/data/gtiff/byte_with_xmp.tif out.tif 
-of cog

$ gdalinfo out.tif -mdd all | grep XMP
Metadata (xml:XMP):
      <rdf:li>XMP</rdf:li>

Even

Le 14/11/2024 à 12:39, Luigi Pirelli via gdal-dev a écrit :
> Hi,
>
> I'm struggling to generate a COG maintaining the original (or at least 
> a selected subset of) Exif and XMP tags (I ses that Iptc tags are not 
> propagated at all, but I'm not interested in them).
> I used gda_translate via CLI or python and the best option seems 
> -strict that, theoretically should maintain all original tags.
>
> But some standard tags are propagated and others not!
> e.g.
> Exif.Image.Software yes
> Exif.Photo.CameraOwnerName no
> Exif.Image.Artist yes
> Exif.Image.Copyright yes
> Exif.Image.DateTimeOriginal no
> Exif.Photo.DateTimeOriginal no
> Exif.Image.Model no
> Exif.Image.CameraSerialNumber no
> etc
>
> It is a bug? a feature? if a bug in any case is there a way to 
> override? The reason to find a solution is that adding tags over a COG 
> with "standard" tools like exiftool, exiv2 etc destroy COG structure. 
> So I need to add or modify tags before converting to COG.
>
> any suggestion?
>
> Luigi Pirelli
> mails: luipir at gmail.com
> luigi.pirelli at geobeyond.it
>
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