Pandoc filter to convert math to inline svg using latex and dvisvgm

texsvg.hs

{-# LANGUAGE OverloadedStrings #-}
import Text.Pandoc.JSON
import System.Directory
import System.FilePath ((</>))
import qualified Data.Hash.MD5 as MD5
import qualified Data.Text as T
import System.IO.Temp
import System.Process
import Control.Monad (unless)

main :: IO ()
main = toJSONFilter mathToSvg

mathToSvg :: Inline -> IO Inline
mathToSvg m@(Math mathType x) = do
  let wrap = T.unpack . removeNewline . case mathType of
                   InlineMath -> \x' -> "\\(" <> x' <> "\\)"
                   DisplayMath -> \x' -> "\\[" <> x' <> "\\]"
      preamble =[
          "\\documentclass[border=1pt,varwidth]{standalone}",
          "\\usepackage{standalone}" <>
          "\\usepackage{amsmath}" <>
          "\\usepackage{amssymb}" <>
          "\\usepackage{cancel}" <>
          "\\begin{document}"
        ]
      postamble = [ "\\end{document}" ]
      removeNewline = T.filter (`notElem` ("\r\n" :: [Char]))

  tempDir <- getTemporaryDirectory
  let cacheDir = tempDir </> "pandoc.texsvg.cache"
  createDirectoryIfMissing True cacheDir
  let mathHash = MD5.md5s $ MD5.Str $ show m
      outfilename =  cacheDir </> mathHash <> ".svg"

  fileExists <- doesFileExist outfilename

  unless fileExists $
    withSystemTempDirectory "pandoc.dir" $ \tmpDir ->
      do
        origDir <- getCurrentDirectory
        setCurrentDirectory tmpDir
        _ <- readProcess "latex" (preamble <> [wrap x] <> postamble) []
        _ <- readProcess "dvisvgm"
                 ["-b2pt", "-Z1.2", "-n", "-o", outfilename, "standalone.dvi"] []
        setCurrentDirectory origDir

  svg <- T.pack <$> readFile outfilename
  return $ RawInline (Format "html") $ case mathType of
    InlineMath -> svg
    DisplayMath -> "<p>" <> svg <> "</p>"
mathToSvg x = return x

Hi @lierdakil i try to make a lua filter, but i am a newer in either lua or haskell, and i failed to install pandoc via cabal...thus i try to make a lua version:

local default_template = [[
\documentclass[12pt,preview]{standalone}
{{ preamble }}
\begin{document}
\begin{preview}
{{ code }}
\end{preview}
\end{document}
]]

local default_preamble = [[
\usepackage[utf8x]{inputenc}
\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amstext}
\usepackage{newtxtext}
\usepackage{mhchem}
\usepackage{chemfig}
\usepackage[libertine]{newtxmath}
\DeclareOldFontCommand{\rm}{\normalfont\rmfamily}{\mathrm}
\DeclareOldFontCommand{\sf}{\normalfont\sffamily}{\mathsf}
\DeclareOldFontCommand{\tt}{\normalfont\ttfamily}{\mathtt}
\DeclareOldFontCommand{\bf}{\normalfont\bfseries}{\mathbf}
\DeclareOldFontCommand{\it}{\normalfont\itshape}{\mathit}
\DeclareOldFontCommand{\sl}{\normalfont\slshape}{\@nomath\sl}
\DeclareOldFontCommand{\sc}{\normalfont\scshape}{\@nomath\sc}
\newcommand{\N}{\mathbb{N}}
\newcommand{\R}{\mathbb{R}}
\newcommand{\Z}{\mathbb{Z}}
]]

function exec_math (elem)
    -- Convert Math El -> DVI via latex --
    mathEq = default_template:gsub("{{ preamble }}", default_preamble):gsub("{{ code }}", elem.text)
    local tex = io.open("input.tex", "w")
    tex:write(mathEq)
    io.close(tex)
    os.execute("latex input.tex")
    os.execute("dvisvgm --no-fonts input.dvi output.svg")
    local svg = io.open("output.svg", "rb")
    if not svg then
        return nil
    end
    local content = svg:read "*a"
    local output
    if elem.mathtype == 'InlineMath' then
        output = content
    else
        output = "<p>" .. content .. "<p>"
    end
    elem = pandoc.RawInline('html', output)
    return elem
end

return {
    { Math = exec_math }
}

but after generating svg with markdown math $\chemfig{C([2]-H)([6]=H)}$ and return a RawInline elem, it still renders a <span class="math inline">$\chemfig{C([2]-H)([6]=H)}$</span>, and log a warning in the console:

[WARNING] Could not convert TeX math \chemfig{C([2]-H)([6]=H)}, rendering as TeX:
  \chemfig{C([2]-H)([6]=H)}
          ^
  unexpected control sequence \chemfig
  expecting "%", "\\label", "\\tag", "\\nonumber" or whitespace

Do you have any idea how to fix it?.....

a google group link pubed by myself.. https://groups.google.com/g/pandoc-discuss/c/4CirnNd-ETs

To begin with, your call to dvisvgm is not quite right... Try using dvisvgm --no-fonts input.dvi -o output.svg. Besides, I'm pretty sure that call to table.insert will fail, since neither argument is a table. I don't think you need it to begin with.

sorry but i find that you're right... as i have read a wrong document... thx:)

Here's my gist https://gist.github.com/PassionPenguin/43fc09b942cedc428ae246bff8b6e193 :)