Bug 456225

Summary:	Rescaling of text is ugly when zooming in or out
Product:	[Applications] okular	Reporter:	jan.claussen10
Component:	general	Assignee:	Okular developers <okular-devel>
Status:	REPORTED ---
Severity:	wishlist	CC:	aacid, miranda, nate, tbertels
Priority:	NOR
Version First Reported In:	22.04.2
Target Milestone:	---
Platform:	Manjaro
OS:	Linux
See Also:	https://bugs.kde.org/show_bug.cgi?id=437401
Latest Commit:		Version Fixed In:
Sentry Crash Report:

Description jan.claussen10 2022-07-02 00:19:16 UTC

SUMMARY
Text is kind of wobbly when zooming in our out. Some lines disappear and reappear. It is just not very pleasant to look at. With the rise of Plasma mobile these touch gesture issues should get fixed at some point


STEPS TO REPRODUCE
1. Zoom in or out slowly
2. Observer the text

OBSERVED RESULT
Text is wobbly and ugly while zooming

SOFTWARE/OS VERSIONS
KDE Plasma Version: 5.24.5
KDE Frameworks Version: 5.95.0
Qt Version: 5.15.5

ADDITIONAL INFORMATION

Comment 1 Nate Graham 2022-07-05 16:35:47 UTC

What method are you using to zoom that makes this issue visible? A pinch gesture on your touchscreen?

Comment 2 jan.claussen10 2022-12-10 11:48:14 UTC

Sorry, have not read the mail I guess. It occurs in both situations. When zooming with a pinch gesture, it occurs much more though.

Comment 3 Thomas Bertels 2024-04-11 12:11:38 UTC

The problem is that Okular doesn't use any interpolation while zooming in or out. When the zooming is done, the text then gets re-rendered.
This can be easily reproduced by zooming in or out using Ctrl+mouse wheel.

Lanczos 3 or 4  should be used when zooming in or out.
An option could be added to select bilinear for slower computers.

Comment 4 Thomas Bertels 2024-04-11 12:12:12 UTC

*** Bug 473470 has been marked as a duplicate of this bug. ***

Comment 5 Albert Astals Cid 2024-04-22 14:27:49 UTC

This is not a bug, obviously the text needs to be re-rendered when zooming in or out

Comment 6 jan.claussen10 2025-09-25 10:24:58 UTC

Well, may it be technically a bug or not, it definitely looks quite ugly and makes for a bad user experience. No other PDF reader I have ever seen does it like this. If there is really no interest in improving this, I guess I will have to accept it, but I think this would be an important improvement.