nextcloud/apps/theming/README.md

Theming

Background picture requirements

A reference to why it was very difficult to actually find good background pictures – there are quite some requirements when it comes to picking:

• It needs to be an exceptionally good photo of course – since when chosen, people will see it every day.
• We need to have a good balance of different motives, e.g. not too many landscape pics.
• Same for a good balance of different colors.
• The photo needs to work as a background. Photos with objects focused in the middle don’t really work as they will be overlapped by the widgets and content anyway.
• Especially the top part cannot have too much differing contrast, as then it’s not possible to see the navigation icons.
• Especially the top part should be either dark-ish or light-ish, but not a shade exactly inbetween because then contrast can neither be achieved with light nor dark icons.
• We serve the pictures at 4k resolution and most of the selected images are also available in 6k or higher so it is future-proof.
• For the search of course we had to limit to CC0, CC By and CC By-Sa. Only CC0 would have been practically impossible cause there’s just not so many good ones which fit.
• Good pages to find photos are StockSnap, Wikimedia Commons, Openverse and Flickr (with license “commercial use & mods allowed”), sorting by interesting or downloads. Most others like Unsplash, Pexels, Pixabay, etc. meanwhile have a non-standard license.

Background picture technicals

• All backgrounds are sized to maximum 3840px width (4K resolution).
• To ensure quick loading times, the image needs to be compressed, ideally to around 1 MB or less. E.g. via 90–95% quality in GIMP export. We could also explore using newer formats.
• Previews are sized to 352px width (min height 192px), which is double of the current picker grid size so it looks nice on high-res displays. Quality is also set to around 90% at export.

Background picture credits

In img/background/:

• Default background: Clouds (Kamil Porembiński, CC BY-SA) – original 4k, color modified and sky color changed to Nextcloud blue.
• Default dark mode background: Pedra azul milky way (Eduardo Neves, CC BY-SA) – original 5k.
• Soft floral (Hannah MacLean, CC0) – original 5.5k.
• Morning fog (Ted Moravec, Public Domain) – original 3k.
• Underwater ocean (Stefanus Martanto Setyo Husodo, CC0) – original 5k.
• Rhythm and blues (Zoltán Vörös, CC BY) – original 2k (it’s fine since the motive is blurry anyway).
• Butterfly wing scale (Anatoly Mikhaltsov, CC BY-SA) – original 5k, cropped to use top right and retouched away a bright spot, now 4k.
• Cetonia aurata take off composition (Bernie, Public Domain) – original 8k.
• Ribbed red metal (Dejan Krsmanovic, CC BY) – original 5k.
• Barents bloom (European Space Agency, CC BY-SA) – original 2k (it’s fine since the motive is blurry anyway), rotated 90° right.
• Flippity floppity (Hannes Fritz, CC BY-SA) – original 4k, cropped to top left (2k) so the sharp parts are not part of the photo, looks better.
• Roulette (Hannes Fritz, CC BY-SA) – original 4k.
• Sea spray (Hannes Fritz, CC BY-SA) – original 6k.
• New zealand fern (Bernard Spragg, CC0) – original 2.5k.
• Pink tapioca bubbles (Rawpixel, CC BY) – original 6k.
• Waxing crescent moon (NASA, Public Domain)
• Cityscape (Tommy Chau, CC BY) – original 6k.
• Lion rock hill (Tommy Chau, CC BY) – original 6k.
• Yellow bricks (Lali Masriera, CC BY) – original 4k, color modified for visibility of icons, and slightly cropped on the left so motive is centered.