[tex4ht] Picture generation with LuaTeX

[Michal Hoftich]

Hi all,

there was a question on TeX.sx [1] asking for picture generation
support with OpenType fonts. As you may know, it was quite hard to add
support for OpenType fonts, it is basically a hack. Due to way this
support works, it is not possible to generate pictures using \Picture+
or \Picture* commands which contains Unicode characters (basic ASCII
or math should be fine). These characters are replaced just with "x"
characters.

I've came with solution which involves loading of `tex4ht` in the PDF
mode and converting images from PDF [2]. It was quite involved
process, but I found that it is indeed possible to work in the PDF
mode. I think that it would be also possible to produce directly HTML
if used together with Lua4ht.

I need to clean it a bit and produce an extension for make4ht from the
code. The more detailed description is in the answer [2], I hope
someone will find it useful.

Best regards,
Michal

[1] https://tex.stackexchange.com/q/447602/2891
[2] https://tex.stackexchange.com/a/447852/2891