Created attachment 151820 [details] PDF test file for Data Matrix Code SUMMARY *** NOTE: If you are reporting a crash, please try to attach a backtrace with debug symbols. See https://community.kde.org/Guidelines_and_HOWTOs/Debugging/How_to_create_useful_crash_reports *** STEPS TO REPRODUCE 1. Open with Okular a PDF file which contains small Data Matrix Codes (similar to QR Code) 2. If this Data Matrix Code is small then you will notice a bad rendering (blurry rendering), much more noticeable when printing on black and white laser print. 3. Open the same PDF with another PDF reader (Xpdf, firefox PDF reader) : you will notice better rendering, sharp rendering OBSERVED RESULT Blurry Data Matrix Codes on screen display and on black and white laser print for small Data Matrix Code EXPECTED RESULT The Data Matrix Code should be sharp, like other PDF reader. SOFTWARE/OS VERSIONS Linux/KDE Plasma: Arch linux (available in About System) KDE Plasma Version: 5.25.4 KDE Frameworks Version: 5.97.0 Qt Version: 5.15.5 ADDITIONAL INFORMATION Another way to reproduce the problem : buy PDF stamps on french La Poste website : https://www.laposte.fr/mon-timbre-en-ligne These stamps have small Data Matrix code, Okular doesn't manage to display them with accuracy, we can see blurry rendering, both on screen and on laser print. You can also open the attached file "GS1_DataMatrix_Guideline.pdf" with okular, on page 20 you will notice that the data matrix code is bad rendered (blurry areas) if you compare with PDF firefox reader or Xpdf the rendering is much better. Data Matrix code on wikipedia : https://en.wikipedia.org/wiki/Data_Matrix
Okular doesn't do any PDF rendering. Please report the issue at https://gitlab.freedesktop.org/poppler/poppler/-/issues/new?issue
(In reply to Albert Astals Cid from comment #1) > Okular doesn't do any PDF rendering. > > Please report the issue at > https://gitlab.freedesktop.org/poppler/poppler/-/issues/new?issue Not sure if poppler is the culprit, as it is used also by Xpdf, and Xpdf doesn't have problem for rendering data matrix code.
I created a bug report for poppler : https://gitlab.freedesktop.org/poppler/poppler/-/issues/1291 But as I said I am not sure if poppler is the root cause, I think Okular may not use correctly poppler (bad parameters when calling poppler API ?)
Created attachment 151859 [details] Comparison between Okular and Xpdf for rendering Data Matrix image. Here is a comparison between Okular and Xpdf for rendering Data Matrix image, we can see that Okular doesn't manage to display correctly the data matrix, it's a little blurry.
xpdf does not use poppler. Instead, poppler is a (partial) fork of xpdf. The two codes are similar but not identical. To convince yourself that poppler is the culprit try to render the file with `pdftoppm`.