Created attachment 176055 [details]
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Created attachment 176056 [details]
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Thank you for your bug report!

Debian advises users to not submit bugs upstream (https://www.debian.org/Bugs/Reporting), as this version of the KDE software is out of support from KDE, and so it's possible that the bug exists only in Debian at this point.

Could you report the bug to Debian using the report bug utility (https://packages.debian.org/stable/utils/reportbug)? If necessary, the maintainer of the package will forward the bug upstream.

Thanks for understanding!

I'd rather wait until Debian (finally ...) gets 6.x into testing and then report in back here, working indirect through distro maintainers proved to slow things down unnecessary.

Did you test it and have reason to believe it was fixed in more recent versions?
It is not that important for me right now, but I think if the bug is still present in current versions, it should be addressed.

(In reply to Alex from comment #4)
> I'd rather wait until Debian (finally ...) gets 6.x into testing and then
> report in back here, working indirect through distro maintainers proved to
> slow things down unnecessary.
> 
> Did you test it and have reason to believe it was fixed in more recent
> versions?
> It is not that important for me right now, but I think if the bug is still
> present in current versions, it should be addressed.

The intent of Debian's model is to have everything work through their maintainers, though - the perceived slowness there is necessary in their approach so that their team can arrange the whole operating system together as they see fit. So, if it doesn't go through their maintainers, then it may never get fixed in the Debian version you're using as they are generally not adopting new upstream versions of KDE software (they generally only "pull" individual patches as they see fit, rather than whole new versions of KDE software getting "pushed").

I appreciate your looking toward the future of the software - when using Debian, the best way to test how current versions are working and report upstream bugs would likely be to use a Flatpak version (which is in sync with the most current release) and test it there, rather than any Debian-packaged versions. If the same behavior exhibits itself in the Flatpak, then this would definitely make sense to re-open based on the current software version.

I'm not motivated to go through the Debian process with this now. They may or may not get a backported fix, but hopefully they will get plasma 6 "soon" and I guess they'll probably they will ask me to wait until then.

I would suspect though that the problem might be present in current Gwenview (you know better if someone relevant got changed in the meantime or not) and willing to work with you to reproduce and test it.
I still have a other bugs on hold (but open) waiting for Plasma 6 in Debian, but if it is closed I do not know if I will still think of it when Debian finally manages to get recent KDE apps into testing (or even unstable).

Did you try to reproduce the bug on your system? Maybe then I don't even need to give feedback again once Debian gets newer packages. I suppose the problem is straightforward to add something along the lines of .convert("RGBA") before displaying or zooming, so scaling doesn't need to add dithering to reproduce the interpolated colors.

(In reply to Alex from comment #6)
> I'm not motivated to go through the Debian process with this now. They may
> or may not get a backported fix, but hopefully they will get plasma 6 "soon"
> and I guess they'll probably they will ask me to wait until then.
> 
> I would suspect though that the problem might be present in current Gwenview
> (you know better if someone relevant got changed in the meantime or not) and
> willing to work with you to reproduce and test it.
> I still have a other bugs on hold (but open) waiting for Plasma 6 in Debian,
> but if it is closed I do not know if I will still think of it when Debian
> finally manages to get recent KDE apps into testing (or even unstable).
> 
> Did you try to reproduce the bug on your system? Maybe then I don't even
> need to give feedback again once Debian gets newer packages. I suppose the
> problem is straightforward to add something along the lines of
> .convert("RGBA") before displaying or zooming, so scaling doesn't need to
> add dithering to reproduce the interpolated colors.

I'm not a Gwenview developer, just trying to help triage bugs and make sure that developers have workable bugs in front of them when they're able to work on them, so I wouldn't inherently know better than anyone else.

On that note, apparently none of the PNGs I had did have indexed colors (I'm not a graphics person!) but I tried creating one and did actually see what you described still show up in the current version.

You definitely seem to understand a good bit about how the image processing side of things works - the suggestion on approaches to processing differently are helpful, thanks!

And on the Debian front, I think it is tough sometimes to keep things smooth between a project that intends to move slowly on features and do patches on top of existing versions (Debian), and a project that moves quickly on new feature versions and works best when all components move forward relatively quickly (KDE). I'm not a Debian user myself, but I'll just say that without their maintainers in the loop, there may be things they just aren't taking into consideration.

Let's do it another way. I can sometimes test on a KDE Neon system, if you still need me to reproduce on the latest version.

I only supposed that this is kind of a bug that is probably present since quite some time because it doesn't occur that often and then is not always that noticeable, so I took the time to report it as many people probably are annoyed by it but just shrug it off. I try to also report such minor issues, what doesn't mean that I expect you to fix them right now.

> You definitely seem to understand a good bit about how the image processing side of things works - the suggestion on approaches to processing differently are helpful, thanks!

I guess enough for a rough idea what is probably going on, but I didn't look into the code myself yet. But from my guess the maintainers can probably find out quite easily.

Regarding Debian: I am waiting since months for them to pick up Plasma 6, especially I would like to re-test some Wayland issues, but I don't blame them for their considerate process when I chose Debian (testing) myself. But they seem to have enough blockers themself such that I won't expect them to take on such a bug in a timely manner, so I guess as long as it doesn't really look like an integration problem in Debian, the only question for the upstream is if the bug was fixed in newer versions.

Thanks for testing!

Hello. I think this issue is very simlate to https://bugs.kde.org/show_bug.cgi?id=459627. 
I hear to many people said to i found strange artifact in png image.  me too. 
And fix patch complete merge. This fix patch contribute of good code developer. You can see this.
https://invent.kde.org/graphics/gwenview/-/merge_requests/293#note_1071225
So i think this issue status is waiting on new version of maybe gwenview 24.12. 

Debian is stable OS, but very slow update.
Q. When gwenview 24.12 on debian? 
A. Debian is need more long time then other linux distribution. That's how slow it is.

So if you think this issue similar 459627. You can status change RESOLVED. Please that it.

(In reply to SkyWalteron from comment #9)
> Hello. I think this issue is very simlate to
> https://bugs.kde.org/show_bug.cgi?id=459627. 
> I hear to many people said to i found strange artifact in png image.  me
> too. 

Great catch, thanks!

*** This bug has been marked as a duplicate of bug 459627 ***