There is nothing wrong with generating the epub file with the following code:
\documentclass{ctexart}
\begin{document}
Hello World
$x_1$
\end{document}
$ tex4ebook -f epub3 ./demo.tex
But when inserting unicode characters:
\documentclass{ctexart}
\begin{document}
你好！世界！
\end{document}
The following error occurs:
[STATUS] tex4ebook: Conversion started
[STATUS] tex4ebook: Input file: ./demo.tex
--- warning --- Couldn't find font `unisong75.htf' (char codes: 0--255)
----------------------------------------------------
environment file
----------------------------------------------------
% unix/tex4ht.env (2019-03-07), generated from tex4ht-env.tex, and
% modified by hand for TeX Live (unix).
% Copyright 2009-2019 TeX Users Group
% Copyright 1997-2009 Eitan M. Gurari
%
% This work may be distributed and/or modified under the
% conditions of the LaTeX Project Public License, either
% version 1.3c of this license or (at your option) any
% later version. The latest version of this license is in
% http://www.latex-project.org/lppl.txt
% and version 1.3c or later is part of all distributions
% of LaTeX version 2005/12/01 or later.
%
% This work has the LPPL maintenance status "maintained".
%
% The Current Maintainer of this work
% is the TeX4ht Project <http://tug.org/tex4ht>.
%
% If you modify this program, changing the
% version identification would be appreciated.%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Notes: %
% 1. Empty lines might be harmful %
% 2. Tagged script segments <tag>...</tag> are scanned only if %
% their names are specified within -ctag switches of tex4ht.c %
% and t4ht.c. When -c switches are not supplied, a -cdefault %
% is implicitly assumed. %
% The tags <tag> and </tag>, but not their bodies, are %
% ignored if they are not located at the start of their lines. %
% 3. Place this file in your work directory and/or root directory %
% and/or in directory `xxx' of your choice. In the latest case, %
% compile tex4ht.c and t4ht.c with `#define ENVFILE xxx', or %
% provide the address of the file to tex4ht and t4ht throught %
% the -e switch %
% 4. Under kpathsea, the substring `%%~' may be employed in %
% commands to indirectly obtain the value of ${TEXMFDIST}. %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
% * Replace `path', and possibly what follows, with appropriate %
% content %
% * A path may start with: %
% ~ for environment variable HOME %
% ~~ for environment variable TEX4HTTFM %
% %%~ for ${TEXMFDIST} of KPATHSEA %
% * A ! requests recursive search into subdirectories %
% * Multiple t and i entries are allowed %
% * When supported by kpathsea %
% + t entries are ignored %
% + the path before /ht-fonts/ is ignored in i records that don't %
% represent real addresses %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%
tpath/tex/texmf/fonts/tfm/!
......
----------------------------------------------------
--- warning --- Couldn't find font `unisong4e.htf' (char codes: 0--255)
--- warning --- Couldn't find font `unisongff.htf' (char codes: 0--255)
--- warning --- Couldn't find font `unisong59.htf' (char codes: 0--255)
--- warning --- Couldn't find font `unisong4f.htf' (char codes: 0--255)
What should I do to make tex4ebook support unicode characters?
