Integrate with nc tags global

[yekibud]

A first iteration on integrating metadata with NC tags (refs #20). (Keep in mind that I haven't written a line of PHP for 15 years and I've never hacked on the NC code-base before - so please excuse any noob mistakes, and all pointers are welcome.)

This first iteration only supports IPTC Keywords and automatically extracts, creates and assigns tags for all NC user image files with a queued background job (upon nextcloud-metadata install or update). It also adds a file create/update hook for extracting/creating/assigning tags after initial installation.

This is the primary itch I have to scratch for image file/NC tag integration. But there are clearly more features that would support more users, such as:

• persist personal settings to db table for more supported metadata properties
• fetch db table/selected options for Hook
• trigger queued job if "write tags for existing files?" personal setting selected
• also trigger job when new metadata options selected

Rather than focus on those features at this time I would rather scratch my secondary itch, which is the fact that nextcloud-photos does not support sharing photos by tag - which it clearly should. With both nextcloud-photos and nextcloud-metadata updated for both features, we would have a complete solution for a major use case for users who manage their photos with IPTC Keywords (such as with Shotwell), and then like to share photos based on those tags.

Thoughts?

[yekibud]

Created a related issue in nextcloud/photos#360

[yekibud]

Well, @gino0631 , you can probably go ahead and close this PR, unless you want any of the changes, since I just ran into a bit of an upstream wall (see nextcloud/photos#360).

The main use-case/itch I have to scratch is using image metadata to organize photos and subsequently share these collections. It turns out there is a sufficient solution using Piwigo synchronized with NC file storage, so I think I'm going to go with that for now and drop work on NC photos.

[Bugsbane]

This patch would be incredibly useful to anyone using other tools with the photos in Nextcloud. Personally I would like to have Photoprism automatically tag people, places etc in my photos, but Nextcloud just ignores all the tags created. Others use photomanagement apps and the tagging features now in every major operating system (Windows, Mac and Linux). Even if I tag something in Nextcloud, download and reupload, all of the Nextcloud tags disappear. This wouldn't happen if NC added it's tags also to the IPTC keywords and this patch was applied.

I can't speak to the quality of the code. It would just be such a huge shame if such a useful feature -with code written for it no less - got thrown out just because no one looked at merging it.

[gino0631]

The proposed patch creates Nextcloud tags from Metadata Keywords, it doesn't add Nextcloud tags to picture metadata. Also, I wouldn't be sure that doing the update in a background job is a good idea because of the performance reasons. Otherwise, the idea looks good.

[maksymov]

any news with this?

[gino0631]

@maksymov thanks for the ping, no news so far unfortunately