Following a thread on GitHub regarding the jpeg_quality setting of the previewgenerator app.
I found that the jpeg_quality setting is not used by Nextcloud (files/gallery) itself, so if you do not use the previewgenerator, all thumbnails and previews will be generated at quality level 90.
As far as I can tell by the source code, this snippet is used to set the quality level:
It is clear that Nexctcloud core is looking for a very similar jpeg_quality setting as the one used by the previewgenerator app. This is not , however, set in the config.php file. It has to be set with the following occ command:
Is this a bug, a feature, or a mistake in previewgenerator app or in the Nextcloud core? This setting (for the Nextcloud core) is not documented anywhere as far as I can tell.
Could be. I see you already comment original Post, thanks!
Also I set it as was written in the article and newly generated jpegs are dramatically smaller in compare to older with the same resolution. Seems those settings are working somehow.
Yes, the jpegs are smaller because the original settings in the article affects the third party app “previewgenerator”. So while you run that in the background to pre-render previews that setting takes effect. However, if you just browse around with the files app, then it will make much larger files.