[gdal-dev] New OGR driver: Imageset

Even Rouault even.rouault at mines-paris.org
Tue Jul 24 09:25:50 PDT 2012

> Even,
> I'm not convinced that a distinct EXIF domain is the best way to go.
> Non-default metadata domains are often not carried with images
> during translation or other processing and are (imho) more appropriate
> for data that would no longer apply to transformed imagery or that is
> bulky and of very limited interest.
> The EXIF metadata - at least the geolocation portions - is very relevant
> even after many kinds of transformation, is not too bulky and is very
> interesting to preserve.  Instead i'd be inclined to identify the EXIF
> info as "well known" metadata names for the default domain.

I'm OK to expose the decyphered content of TIFFTAG_EXIFIFD and TIFFTAG_GPSIFD in
the default domain if you think it is more appropriate. There should be no
technical difficulty, and it should not cause any particular performance problem
to do so.

The only point that might be a bit confusing, if they are exposed in the default
domain, is that if they gdal_translate a TIFF that has EXIF/GPS info to another
TIFF, they will be preserved as "standard" GDAL metadata (in the
TIFFTAG_GDAL_METADATA specific tag). So a user that will do gdalinfo on the
resulting TIFF will not realize that the metadata comes from the GDAL tag, and
that it will not be usable by applications that use EXIF/GPS tags. But that can
be documented as a limitation in the GTiff format page.

Or we could choose to strip EXIF_* items when writting them in
TIFFTAG_GDAL_METADATA to avoid that confusion ? Of course, the best would be to
implement write support for EXIF/GPS tags, but that's another story...

> Best regards
> --
> ---------------------------------------+--------------------------------------
> I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
> light and sound - activate the windows | http://pobox.com/~warmerdam
> and watch the world go round - Rush    | Geospatial Software Developer

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