Fresh install of Fedora Workstation and updated to latest 6.2
When I press F11 in Dolphin, the “Information Panel” opens and displays a large icon rather than rendering the image for PNG, AVIF, WebP and possibly more image formats. Oddly, it renders the contents of folders that contain these image formats, so I’m guessing it’s a setting I’ve made somewhere.
I seem to have all the relevant codecs installed.
But maybe it’s something to do with Fedora being weird about licences, it’s quite confusing with all the freeworld stuff.
Previews are provided by /usr/share/thumbnailers/ and kio-extras thumbnail plugins.
The plugins are used by default, but the “image” one does not explicitly declare supporting heif/webp because their support might not be present on the system (i.e qt image plugins), despite it might well work.
Here it seems your /usr/share/thumbnailers/ are not working and deactivating them made their preview be rendered by the default image plugin Images (GIf PNG, BMP... in the file type list.
tldr; Check your thumbnailers in /usr/share/thumbnailers/ work and their dependencies executables are installed, or removes the concerned files.
If you tried to launch dolphin from the command line you might have got some output hinting this way.
So I can consider this a bug, we probably want to use the standard thumbnailer to read those files, just not store it to cache and remove their file after use.
I think a good solution, for me, will be to convert the webp and avif and heic stuff to max res jpg and be done with it. Make things easier to sort too.
You were just lucky, a dolphin maintainer was around, but discussions on discuss can fade or buried in noice, whereas bugs.kde.org keeps everything and categorize things.
The bug report could be reported for kio:
The information panel missing heif/avif images.
or more precisely:
Previewjob does not use standard thumbnailer when caching is not on.
At the cost of disk space and some amount of quality loss (as those formats are not lossless). If you are patient, it should be fixed in a month or two.
In plasma 6.2.2, the problem is at two places: information panel in Dolphin and also the preview panel in open/save dialogs, they fail to show preview of some formats like heif, png
While previews of png, heif… are correctly generated in the regular view inside Dolphin.
Running Dolphin from terminal shows the following errors: kf.coreaddons: "Could not find plugin gdk-pixbuf-thumbnailer" kf.coreaddons: "Could not find plugin heif"
In plasma 6.2.2, the problem is at two places: information panel in Dolphin and also the preview panel in open/save dialogs, they fail to show preview of some formats like heif, png