Previews sometimes looks pixelized

[skjnldsv]

Because we generate previews with size in power of 4, the images preview are loaded with 256px. The next step is 1024 which is a lot more data to load

cc @jancborchardt @rullzer

[rullzer]

Yeah. This is how it is for now. I have no real solution yet.

[skjnldsv]

Ah, I understand why.

The preview manager use the maximum, meaning if your picture is 2560*1000, and you request for a 256px, instead of being 655x256, it will be 256x100 (which make sense)
But since we're cropping the images and fitting them to a square...

The preview manager have an option to request a square (&a=false) but the cropping is not centered, so maybe we could fix this?
Because this works well in landscapes, but not in portrait

(cropping is done for the width, but not the height: https://github.com/nextcloud/server/blob/5bf3d1bb384da56adbf205752be8f840aac3b0c5/lib/private/Preview/Generator.php#L388)

[skjnldsv]

Just tried it, works nicely!