For Nextcloud v 24 and later, what are the best values for squareSizes, widthSizes and heightSizes in previewgenerator?

I am trying to improve the effectiveness and storage efficiency of the previewgenerator on my nextcloud server. Besides out-sourced the preview generation to imaginary as suggested by Server tuning, I have read many suggestions, both official such as:

and unofficial, such as:

However, they are all years old and seem to be outdated. As the patch ce10f8b merged, nextcloud returns previews of the following sizes only:

  • 64
  • 256
  • 1024
  • 4096

Based on my usage of nextcloud with a Google Chrome (v.106.0.5249.119) on macOS (v.12.6.1) running on iMac 27" 5K as a client, the preview icon sizes on both detailed row view and icon view of Files pane are 21x21 and 132x132 respectively. However, nextcloud requests previews of size 500x500 in both cases. Nonetheless, the actual preview images returned are 1024x1024 in size for both.

Given that I don’t want to restrict the preview size below 1024 as I prefer to look at a higher resolution image when I click on a photo. I wonder:

  1. For Nextcloud v24, what are the best values for squareSizes, widthSizes and heightSizes respectively now? A single “1024” for all 3?
  2. Where are the preview size of 64 and 256 used? For Nextcloud apps on iOS and Android? Other browsers running on non-HD display?

Hello. I’m very curious what people will answer.

Im also tuning my previews.

I’ve noticed that the previewsfolder is huge, most of my pictures and that of my family are Phone Camera pictures and max 3-5MB. The previews are 1-2MB, so completely useless imho.

It got to a point now where my CPU usage is huge for preview creation and the folder is extremely big, but they are actually practically useless (except for thumbnails). There has been no information by devs as to why they wouldnt allow you to disable the preview (so click on pictures would always load the original).

I think I’ll go back to not creating previews, and use photoview on my server to actually look at the photos. (it’s also much much faster than the photo app)

I still don’t get what nextcloud is for, when such a crucial part like pictures, doesn’t seem to be intuitive and fast and highly flexible for admins. But hey, im just a user and not a dev/programmer. I would gladly donate if this stuff would work fluently and efficiently though.

Hello there,

Nextcloud 26 finally introduces a concurrency limit for the built-in preview generation, which solves the issue with the system getting overloaded by preview requests.

Nextcloud >=25 should also be more conservative in the variety of preview sizes; according to the source code, previews are only generated in these sizes: 64, 256, 1024, 4096.
If you also have Imaginary set up, the 64-sized preview is not generated and the 256 is used instead.

As for previewgenerator, you can follow this issue on github: Preview formats no longer sufficient for photo app 2.0.0 · Issue #1492 · nextcloud/photos · GitHub