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

[Javier Jimenez Shaw]

In this PR I tried to pass the XMP data when a TIFF copy or COG was done
https://github.com/OSGeo/gdal/pull/3050
Maybe it was not complete.

On Thu, 14 Nov 2024 at 13:10, Luigi Pirelli via gdal-dev <
gdal-dev at lists.osgeo.org> wrote:

> Tnx Even
>
> I suspected that -strict was not "complete". In any case My first code
> version was adding tags over an already generated COG, but the result was
> an unreadable/broken file in QGIS. I suppose because pyexiv2 is not
> flexible enough and stuck with a rigid version of tiff structure.
> I'll try a workaround using some lib or app able to maintain a readable
> image, tnx for the hint.
>
> Luigi Pirelli
>
>
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>
> On Thu, 14 Nov 2024 at 13:02, Even Rouault <even.rouault at spatialys.com>
> wrote:
>
>> 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
>>
>>
>> **************************************************************************************************
>> * LinkedIn: https://www.linkedin.com/in/luigipirelli
>> * Stackexchange: http://gis.stackexchange.com/users/19667/luigi-pirelli
>> * GitHub: https://github.com/luipir
>> * Book: Mastering QGIS3 - 3rd Edition
>> <https://www.packtpub.com/eu/application-development/mastering-geospatial-development-qgis-3x-third-edition>
>>
>> **************************************************************************************************
>>
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>>
>> -- http://www.spatialys.com
>> My software is free, but my time generally not.
>> Butcher of all kinds of standards, open or closed formats. At the end, this is just about bytes.
>>
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