[Shotwell] How to remove metadata from photo files?

[Thomas Jost]

On Mon, 17 Oct 2011 13:33:06 +0100, Colin Law <clanlaw at googlemail.com> wrote:
> On 17 October 2011 13:21, Thomas Jost <schnouki at schnouki.net> wrote:
> > Hi list,
> >
> > I've been using Shotwell for several months now and I really like it.
> > Lightweight and efficient -- just what I like on my computers running
> > Arch Linux.
> >
> > When I switched to Shotwell, I enabled the option to write tags and
> > other metadata inside the photo files. Since then I realized that it's
> > probably a bad idea when you want to do regular backups. (Right now I'm
> > using unison to backup and sync the DB and pictures on several
> > computers, but I'd like to switch to a real VCS like git/git-annex or
> > boar).
> >
> > So is there a (simple) way to remove these metadata while leaving the
> > pictures intact? I'm perfectly fine with long command lines and
> > shell/Python/Perl scripts, it's just that I don't know where to start
> > and I'm a little lost with all these EXIF, IPTC and XMP things :)
> 
> I don't understand why you would want to remove the metadata.  What
> harm is it doing?

The problem is that if I add a simple tag to a photo, the file will be
modified. As a result, I will have to re-upload it next time I backup my
photos folder. When doing that on 100+ photos, each one more than 4 MB,
it makes a lot of data to upload just for a tag. It would make more
sense to only upload the modified database (a few kB).

(I know rsync and unison have very efficient algorithms to only transfer
the modified part of a file -- but when doing version control, this
still causes troubles because neither Git nor any other VCS that I know
of is capable of efficiently storing multiple version of binary files --
they just keep full copies for every version, which costs a lot of disk
space)

Right now I disabled saving tags to photos, so I can in fact already do
that. But just to be consistent I'd like to remove the tags from my
other photos.

> Note that all digital pictures have such data for the date taken and
> so on.

Of course, and they are much appreciated :) I'd only want to remove
what was added by Shotwell, i.e. tags and titles.

Regards,

-- 
Thomas/Schnouki