Hi Lutz,

> I have written an EXIF library in plain C ("libexif") and some GTK+
> widgets for displaying and modifying EXIF data ("libexif-gtk"). Both
> available on http://libexif.sourceforge.net. I use them to display
> tags in gphoto2 (command-line frontend) and gtkam (GTK+ GUI).

Thereare a couple of other libraries which do pretty much the same
thing -
see the relevant bug numbers in bugzilla (not sure what they are right
I haven't had a chance to look closely at this, but it looks good.

> However, when loading images from a digital camera directly into
> and letting GIMP save the images (i.e. as JPEG files), all EXIF
> information gets lost. In addition, right now, gimp doesn't offer
> to EXIF information when loading JPEG files.

Yup. We use a straight call to libjpeg's header parser, which doesn't
anything about exif. A couple of people (myself and Raphael Quinet)
looking at this with a view to adding support in 1.3 at least about a
and a half ago. Then I moved to France, and that got put on the back
and my computer's still in storage. The last I had done was a very
hack which replaces our call to the header reader with a call which
read exif
information. The next step would have been to specify how that
would be passed over and back between the main gimp and the jpeg
There was some discussion on this, and it was agreed by everyone
(eventually) that parasites were the way to go. So all we need to do
is define
what information would be available in the exif parasite, and how to
get at it.
I spent a bit of time at this writing up a short RFC, but it was
pretty scattered,
and never got finished/posted to the list.

> How do I go about adding EXIF support to gimp? Should I distribute a
> loader for JPEG files that replaces the current one? Submit a patch
> gimp's JPEG loader and configure.in to --enable-exif if
libexif(-gtk) is
> installed?

If you write a wee report which says what exif information you get out
of the file,
and read up on parasites (which is about where I was at 6 weeks ago),
post a
mail to the list with reccommendations, and then code whatever comes
out of
the reccommendations. Until my computer comes out of storage (15th of
I'll be useless to you, but there are otehrs who were interested in
doing this too.
There was a proposal before to have an exif data editor (or even a
parasite editor)
as well, but I reckon the first step is getting the exif stuff read
into some well-defined
structure, and getting it written out to files in the same proper
structure without
destroying it. If we can do that, a generic parasite editor can handle
the editing of
the metadata.

> In any case, how do I save "per-image" (not per-loader) EXIF data?

I'm not sure what you mean by this...

> Lutz

Hope this helps,

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