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Suboptimal rendering of images with text on lowdpi screens

Hello,

when I open a PDF file that contains images with text in them (e.g. scanned pages), the rendering is a bit "ugly" on my lowdpi screen (24", 1920x1200) at some commonly used range of zoom levels.

I only see this with Okular and qpdfview, rendering in Evince, Atril, Zathura is fine.

STEPS TO REPRODUCE

  1. Open attached file "test.pdf" with Okular or qpdfview.
  2. Set zoom level to 75% (or up to ~100%).

OBSERVED RESULT

Text looks "rather ugly". (See also attached screenshot.)

EXPECTED RESULT

Text looks "clearly readable". (Compare screenshot from same document opened in Evince.)

To reproduce this in a clean environment, I was booting live images of Kubuntu 20.04 and KDE Neon (neon-unstable-20200726-1102.iso).

The original bug report on the KDE bugtracker is here: https://bugs.kde.org/show_bug.cgi?id=424817

Kind regards, Jan

Example pdf illustrating the bug (generated with 'img2pdf -o test.pdf test.png')

Source image file from which the test example was generated

Screenshot rendering of test.pdf with Okular (zoom level 75%)

Screenshot rendering of test.pdf with Evince (zoom level 75%)

Edited by Jan Rathmann
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