Albums: Preview image missing when sharing album links

[graciousgrey]

Discussed in #3452

^{Originally posted by dror3go June 5, 2023}
I'm not sure if this is a bug, a change in config that I've missed, a change in behavior or what, but in the past when I shared a link to an album in WhatsApp/Telegram/etc. There was a preview with thumbnails of several pictures from the album.
Somewhere in the past few releases this changed, and the preview shows only the album's name.

Is that the new desired behavior?

[lastzero]

There simply was a / too much in the generated preview image URL. Should be fixed now.

[lastzero]

Even after fixing the URL, it's still not displaying the preview image when sharing. I suspect this could be due to the redirect, which is now delayed.

[lastzero]

I overlooked that path.Join() will break the site URL, so with this change it simply prepends it to the generated path.

[lastzero]

Our development preview and public demo have been updated. It looks good to me now! 👍

[dror3go]

Looks good, thanks a lot!

[lastzero]

With these changes, album share preview images are regenerated whenever changes are made. Change detection does not yet work when an album contains a picture that is later made private without being (directly) removed from an album. Manual changes in the database also do not cause the thumbnail cache to be cleared. For this reason, the cached image now also expires after only one hour instead of one day as before.

In addition, the rendering has been improved so that previews now look like Polaroids rather than simple squares: