Bug 438125

Summary: 100% zoom pixelated with high dpi scaling
Product: [Applications] gwenview Reporter: Kai Uwe Broulik <kde>
Component: generalAssignee: Arjen Hiemstra <ahiemstra>
Status: RESOLVED FIXED    
Severity: grave CC: nate
Priority: VHI Keywords: regression
Version First Reported In: unspecified   
Target Milestone: ---   
Platform: Other   
OS: Linux   
Latest Commit: Version Fixed/Implemented In:
Sentry Crash Report:
Attachments: Comparison

Description Kai Uwe Broulik 2021-06-05 16:17:41 UTC
Created attachment 139024 [details]
Comparison

SUMMARY
The 100% size in Gwenview always reflects the 1:1 pixel size of the image. However, with high-dpi scaling, it becomes pixelated

STEPS TO REPRODUCE
1. QT_SCREEN_SCALE_FACTORS=2 gwenview some.png

OBSERVED RESULT
The image is rendered pixelated at 100%

EXPECTED RESULT
The image is rendered crisp, just like with no scaling.

See comparison screenshot of gwenview run with 2x and with 1x scaling. Probably related to the recent switcheroo to QGraphicsView or something.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: git master as of 2021-06-03
Comment 1 Nate Graham 2021-06-09 16:44:35 UTC
Whoa how did I not notice that?! Now that I see it, I can't un-see it...

Arjen, can you take a look?
Comment 2 Bug Janitor Service 2021-06-10 15:46:34 UTC
A possibly relevant merge request was started @ https://invent.kde.org/graphics/gwenview/-/merge_requests/84
Comment 3 Arjen Hiemstra 2021-06-14 08:55:57 UTC
Git commit d82258c4318188993a428f51e4a205083a121602 by Arjen Hiemstra.
Committed on 14/06/2021 at 08:54.
Pushed by ahiemstra into branch 'master'.

Don't correct zoom level for hidpi, instead correct target rectangle

Otherwise on hidpi we are using effectively scaling down and then up
again, which causes ugly rendering of images.

M  +6    -4    lib/documentview/rasterimageitem.cpp

https://invent.kde.org/graphics/gwenview/commit/d82258c4318188993a428f51e4a205083a121602