I have a piwigo website for family photos. I believe I used to use shotwell on a computer that broke which uploaded the photos to piwigo. I decided to use digikam on my new computer, which is a nice program, but I am pretty confused about  the upload process.

So far as I can work out, digikam uses web services pwg.images.add and pwg.images.addChunk to add images. These don't (so far as I can see) run the normal synchronize after upload, instead it expects the database fields to be sent as part of the POST request. Except for the GPS coordinates - I can't work out how they get populated in the database. Digikam doesn't pass the tags across in the POST request (There is a TODO style comment). They are in the image as IPTC fields, but piwigo doesn't read them, even if they are configured.

The design philosophy of piwigo seems to be that there is a 1:1 mapping between fields. It doesn't ever seem to try other places as a fallback.

So the question is, how to solve this. I could
1) Learn C++ and make digikam send the tags across. This is not trivial as the tags have to be specified as numbers, so would have to be searched and presumably created if they don't exist.
2) Make piwigo look for the iptc tags if in the photo if they aren't passed via the web interface. This seems contrary to the design philosophy of the 1:1 mapping though. (Change add an else clause to pwg.images.php function ws_images_add the if statement. Here.
3) Write a plugin to scan uploaded photos for iptc keywords and insert them into the database so we can use them as tags.

I think I am leaning towards number 3. Does anyone have any better/different ideas?