Created attachment 139919 [details] Rendered by Okular SUMMARY The Ebook rendering of Okular is very bad(Specially Diagrams). If I am not wrong, it uses ebook-tools which has not been updated since 2010. Mupdf does this accurately, and it can be used to render Ebook files in Okular. Ebook File Used a very popular book called "Python for Everybody". https://www.py4e.com/book
Created attachment 139920 [details] Rendered by Mupdf
Not ideal. But another possible backend. https://github.com/futurepress/epub.js/
Python Backend: https://github.com/aerkalov/ebooklib
Gnome Book backend: https://gitlab.gnome.org/GNOME/libgepub
Totally agree with the other commentators. The presentation of books in EPub is horrendous, plus the function to change the background color, to cause less eye fatigue and dry eyes does not work. I would like to add that I don't know what backend is using Calibre, but EPubs look great too. Maybe it could be another alternative to consider, and I don't know if it could be easier to include in Okular since Calibre is a QT app.
I do think that this is a bad bug report. The bug report should describe the problem. The problem is that okular misrenders certain epub files. The problem is not that okular does not use mupdf. Mupdf could be *one* solution to the problem, but there might also be others that would still solve the same.