Hi
As a user -and not a programmer-, I use only
one tool, named
pyftsubset, and with it, only
one command line. For those who question its use, I advise them to try the tool. As mentioned above, I also make use of the list of unicode characters produced by the Calibre editor reports tool.
pyftsubset is part of bigger project named
fonttools. I failed to see who are its five authors and its maintainer. Anyway thanks to them.
I use it with Archlinux, but it can work on many other operating systems as long as you have a recent version of Fontforge and Python (and python-pip for Arch).
Here is some more information about its use. If I understand correctly, by default, it says that it preserves ligatures. As you can read, it's quite an advanced tool.
See its help file in the attachment below.
From my very limited experience, it gave me good results for the two tests I did. One, with a huge Chinese ttf font, two with a standard ttf font. In both case, I have been able to use an Epubcheck compliant EPUB and to read both of them without any problem on my Koreader.
@Toxaris
Perusing through the text, with the finger extended, looking for italic or bold characters, is not an option for me.
I had hoped there could exist some kind of automatic tool to do it. Anyway, if I compare the size obtained for the 120 characters of the regular font (58k) and I presume it would be the same for the italic font if I proceed from the same 120 characters, it still compares with advantage to the 166k and 129k I obtain by other means.