Since I upgraded to media-gfx/digikam-4.10.0, I've noticed digikam doesn't write my captions to the images themselves, just its own database. I finally got fed up with this bug and searched for a solution. It turns out it's known and fixed upstream: https://bugs.kde.org/show_bug.cgi?id=348586 says the bug is in kde-apps/libkexiv2, and the fix is in version >=15.04.3. This is annoying, since digikam 4.10 and 4.12 are in mainline Portage, but the latest libexiv2 in mainline is 4.14.3. The KDE overlay has kde-apps/libkexiv2-15.04.3, and installing that resolves the bug for me. I'd suggest one of the following actions: 1. Move kde-apps/libkexiv2-15.04.3 from the KDE overlay into mainline Portage so the versions of media-gfx/digikam that are already in mainline actually work. 2. Apply the two-line patch from http://quickgit.kde.org/?p=libkexiv2.git&a=commit&h=c82033b16e8e225bd63a325d9c2b0a16450f2775 to kde-apps/libkexiv2-4.14.3 in mainline. I guess another option is technically possible, but suboptimal: 3. Mask >=media-gfx/digikam-4.10.0 as buggy. Reproducible: Always
Perhaps updating the base exiv2 library might also help. https://bugs.gentoo.org/show_bug.cgi?id=552766
Did the exiv2-0.25 update help?
Yes. I still see the bug with media-gfx/exiv2-0.24-r1, kde-apps/libkexiv2-4.14.3, and media-gfx/digikam-4.12.0. I do not see the bug with media-gfx/exiv2-0.25-r1, kde-apps/libkexiv2-4.14.3, and media-gfx/digikam-4.12.0.
Now, in addition to media-gfx/exiv2-0.25, also kde-apps/libkexiv2-15.08.2 and digikam-4.14.0 are in tree.