This Lua filter for Pandoc converts LaTeX math to MathJax generated scalable vector graphics (SVG) for insertion into the output document in a standalone manner. SVG output is in any of the available MathJax fonts.

This is useful when a CSS paged media engine (such as Prince XML) cannot process complex JavaScript as required by MathJax. See: https://www.print-css.rocks for information about CSS paged media, a W3C standard.

No Internet connection is required when generating or viewing SVG formulas, resulting in both absolute privacy and offline, standalone robustness.

• 2021-01-19: SVG caching
• 2021-01-16: Initial release

First, use the package manager of your operating system to install pandoc, nodejs and npm. brew and choco are recommended package managers for respectively macOS and Windows. See: https://pandoc.org/installing.html

$ sudo apt install pandoc nodejs npm
$ sudo dnf install pandoc nodejs npm
$ sudo yum install pandoc nodejs npm
$ brew install pandoc nodejs npm
> choco install pandoc nodejs npm

Then, by means of node's package manager npm, install the mathjax-node-cli package. This package comes with the tex2svg executable. Leave out the sudo on Windows.

$ sudo npm install --global mathjax-node-cli
> npm install --global mathjax-node-cli

To be used as a Pandoc Lua filter. MathML should be set as a fallback with the --mathml argument.

pandoc --mathml --filter='math2svg.lua'

The math2svg filter is entirely configurable over --metadata key value pairs. Ten configuration keys are available with sensible default values. Hence, depending on your system and intentions, not all keys are necessarily required.

This string key value is only required when, on your system, the path to the tex2svg executable of the mathjax-node-cli package is not present in the $PATH environment variable.

The full path to tex2svg can be found with the following command on *nix, respectively Windows:

$ which -a tex2svg
> where tex2svg

These boolean key values specify whether display math, respectively inline math, should be converted to SVG by the filter. The defaults convert display math to SVG, whereas inline math falls back to MathML when --mathml was specified at pandoc evocation. These defaults offer the following benefits:

• MathML output gets generated much faster than SVG output.
• Moreover, MathML is well suited for inline math as line heights are kept small.

This boolean key value controls whether textual annotations for speech generation are added to SVG formula. The default is false.

This boolean key value automatic switches automatic line breaking. The default is true.

This string key value allows to specify a MathJax font different from the default 'TeX' font. The string should correspond to the local directory name of the font in the mathjax-node-cli installation directory. For example, the key value string for the font in /usr/local/lib/node_modules/mathjax-node-cli/node_modules/mathjax/fonts/HTML-CSS/Gyre-Pagella/ would simply be Gyre-Pagella.

This positive integer key value sets the ex unit in pixels. The default value is 6 pixels.

This positive integer key value sets the container width in ex units for line breaking and tags. The default value is 100 ex.

This string key value allows to load one or more comma separated MathJax extensions for TeX and LaTeX present on the system. These MathJaX extensions reside in a subdirectory of the mathjax-node-cli installation directory.

Take for example, the installation directory of the extensions is /usr/local/lib/node_modules/mathjax-node-cli/node_modules/mathjax/unpacked/extensions/ It contains a subdirectory TeX with the extension file AMSmath.js. This MathJaX extension can be loaded by specifying the string 'TeX/AMSmath' as the value of the math2svg_extensions key.

Caching avoids repetition of the SVG rendering of identical math formulas, both for display and inline math. Caching is on by default.

It might turn out useful to systematically include LaTeX macros, for example as shown below, a series of \newcommand.

---
header-includes: |
    \newcommand{\j}{\text{j}}
    \newcommand{\e}[1]{\,\text{e}^{#1}}
...

This may be achieved either by adding a YAML block with the header-includes key value at the top of the input document, or by having a separate YAML document loaded before the input document. In the latter case, simply evoke pandoc as follows:

pandoc --mathml --filter='math2svg.lua' header-includes.yaml input.md

When automatic equation numbers are desired, these need to be added using cascading style sheets (CSS), as JavaScript is not available in CSS paged media.

Below example CSS code centers display math whilst adding equation numbers to the right.

span.math.display {
    display: flex;
    justify-content: flex-end;
    align-items: center;
    }

span.math.display svg {
    margin: 0 auto;
    max-width: 85%;
    }

span.math.display:after {
    counter-increment: equation;
    content: '(' counter(equation) ')';
    font-weight: bold;
    }

No Internet connection is established when creating MathJax SVG code using the tex2svg command of mathjax-node-cli. Nor will any Internet connection be established when viewing an SVG formula.

Hence, formulas in SVG can be created and viewed offline whilst remaining private.

For code auditing, see also:

• https://github.com/mathjax/MathJax-node
• https://github.com/pkra/mathjax-node-sre
• https://github.com/mathjax/mathjax-node-cli

Copyright (c) 2020-2021 Serge Y. Stroobandt

MIT License

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

$ echo c2VyZ2VAc3Ryb29iYW5kdC5jb20K |base64 -d