Created attachment 135484 [details] Gray scale text in Okular SUMMARY Okular ignores system-wide setting for sub-pixel rendering, i.e. it uses grayscale instead of RGB, for example. STEPS TO REPRODUCE 1. Open any PDF file, scrot it, zoom the resulting file or just zoom using Plasma's Zoom effect. 2. Do the same, but open the file in Kate. 3. See the difference. OBSERVED RESULT Grayscale rendering for text in Okular. EXPECTED RESULT Okular is supposed to follow explicitly set system settings, or have some configuration preference for this, if that's set this way for some reason. SOFTWARE/OS VERSIONS Linux/KDE Plasma: (available in About System) KDE Plasma Version: 5.20.5 KDE Frameworks Version: 5.78.0 Qt Version: 5.15.2 ADDITIONAL INFORMATION On my system text opened in Okular is less readable than the same text opened with e.g. WPS PDF reader due to the above-described issue(/feature?).
Created attachment 135485 [details] RGB scale in Kate
Oh and btw. Bug 418363 seems to be caused by the same or similar thing. I've just zoomed the window of KInfoCenter in, and those "blurry" items I reported are rendered using gray scale, while other text is RGB.
okular doesn't do any PDF rendering. Poppler does pdf rendering.
You can set certain aliasing settings in "preferences -> performance". They are not tied to any system-wide settings, though.
Can confirm that I also have only grayscale rendering in documents displayed by Okular allthough subpixel hinting is enabled in system settings. The difference is very subtle for me though, I didn't notice that before and had to view screenshots at high zoom level to confirm.
Turns out this is a quite interesting issue. Thing is, such behavior is observed in other distros, such as Fedora (Plasma), Ubuntu (Gnome, with its PDF viewer, I don't remember its name, but it doesn't actually matter). Haven't checked openSUSE though. Looks like it's Poppler's fault then.