The Dashboard already does this correctly, and as discussed with @juliushaertl we should use the same logic for the other pages. Specifically, this applies to these 4 backgrounds:

• bernie-cetonia-aurata-take-off-composition.jpg
• lali-masriera-yellow-bricks.jpg
• rawpixel-pink-tapioca-bubbles.jpg
• tommy-chau-lion-rock-hill.jpg

The logic seems to be with the --primary-invert-if-bright variable as far as I can see.

Correct in Dashboard – I would additionally say that we need to invert the logo as well (only if it is our default Nextcloud logo though) cc @karlitschek

Needs to be adjusted in the other apps. I assume with Julius’ move of the header to Vue this might be easier?