mdx-math-svg 1.1.0

SVG Math extension for Python-Markdown

mdx_math_svg

Python-Markdown extension to render equations as embedded SVG.
No MathJax, no images. Real vector drawings.

The resulting static pages load fast and will not reflow as equations are formatted.

The Markdown syntax recognized is:

$Equation$, \(Equation\)

$$
  Display Equation
$$

\[
  Display Equation
\]

\begin{align}
  Display Equations
\end{align}

Installation

Dependencies

Requires Python 3.6 or newer (I presume, to be tested) and Python-Markdown 3.0 or newer, as well as a LaTeX installation. If you don't have LaTeX, I recommend TeX Live.

The extension uses the latex and dvisvgm commands, which should both be installed with your LaTeX distribution. Make sure these programs are on the path so that they can be found.

Install from PyPI

pip install mdx_math_svg

Install locally

./setup.py build
./setup.py install

Usage

Quick and simple

The simple way to add the extension to the Python-Markdown parser is as follows:

import markdown

extension_configs = {
  'mdx_math_svg': {
    'inline_class': 'math',
    'display_class': 'math'
  }
}
md = markdown.Markdown(extensions=['mdx_math_svg'], extension_configs=extension_configs)

See below for a list of all configuration options. This does not allow you to use the SVG cache, use the preferred method below instead.

Preferred method

The preferred method allows you to use the cache. The cache will avoid rendering the same LaTeX equations over and over again every time you rebuild your Markdown content. Only new or changed equations will be rendered.

import markdown
import mdx_math_svg

# Create Python-Markdown instance
math_svg_extension = mdx_math_svg.MathSvgExtension(inline_class='math', display_class='math'),
md = markdown.Markdown(extensions=[math_svg_extension])

# Load cache (if it's there)
math_cache_file_name = 'math_cache'
math_svg_extension.latex2svg.load_cache(math_cache_file_name)

# Use Python-Markdown instance
md.convert("My Markdown text")

# Save cache
math_svg_extension.latex2svg.save_cache(math_cache_file_name)

Load the cache file before you begin any Markdown parsing, and save the cache file when you're done with all of the conversion. Any SVG that was in the cache but was not needed this session will be deleted from the cache. Therefore, you should never re-use the cache among different projects, each project should have its own cache.

Configuration parameters

The extension recognizes the following parameters:

• inline_class: Inline math is SVG wrapped in a <span> tag, this option adds a class name to it. Defaults to the empty string.
• display_class: Display math is SVG wrapped in a <div> tag, this option adds a class name to it. - Default: ''" Defaults to the empty string.
• smart_dollar: Use MathSvg's smart dollars. Defaults to True. See below for an explanation.
• block_syntax: This is an array that chooses which of the block syntaxes are recognized: "dollar" ($$...$$), "square" (\[...\]), and/or "begin" (\begin{env}...\end{env}). Defaults to ['dollar', 'square', 'begin'].
• inline_syntax: This is an array that chooses which of the inline syntaxes are recognized: "dollar" ($...$), and/or "round" (\(...\)). Defaults to ['dollar', 'round'].
• fontsize: Font size in em for rendering LaTeX equations. Defaults to 1, matching surrounding text, usually. Depending on the font used, you might want to increase or decrease this value a bit.

There are other things that can be configured with a bit more difficulty. The math_svg_extension.latex2svg.params variable is a struct containing the following:

math_svg_extension.latex2svg.params = {
    'fontsize': 1,  # em (in the sense used by CSS)
    'template': r"""
\documentclass[12pt,preview]{standalone}
{{ preamble }}
\begin{document}
\begin{preview}
{{ code }}
\end{preview}
\end{document}
""",
    'preamble': r"""
\usepackage[utf8x]{inputenc}
\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{newtxtext}
\usepackage{newtxmath}
""",
    'latex_cmd': 'latex -interaction nonstopmode -halt-on-error',
    'dvisvgm_cmd': 'dvisvgm --no-fonts --exact',  # Has '--precision=2' added if the dvisvgm version is >= 2.2.2
    'libgs': None,  # Gets set through environment variable or default location
}

By changing these values, it is possible to change the preamble, and the options passed to latex and dvisvgm.

The libgs value contains the path to the Ghostscript library. If it cannot be found through the LIBGS environment variable, you can manually set it.

Formatting equations

We'll assume that you know how to write equations in LaTeX. This extension loads the amsmath, amsfonts and amssymb packages in LaTeX.

Inline equations can (by default) be enclosed in single dollar signs ($x$) or escaped parenthesis (round brackets, \(x\)). Note that the dollar signs are "smart" (by default), in that it is required for them to touch the equation on both sides. That is, no spaces are allowed in between the dollar signs and the contained equation. $ x$ or $x $ will not be recognized as an equation. This is to prevent sentences such as "I owe you $1.75 and you owe me $2.50" to be incorrectly recognized as inline equations. This is configured with the smart_dollar parameter.

Block equations can (by default) be enclosed in double dollar signs ($$xxx$$), escaped square brackets (\[xxx\]), or any of the LaTeX environments that start math mode, for example \begin{align} xxx \end{align}. Block equations must have one empty line before and one after, and cannot have any empty lines inside. There should be nothing before or after the enclosing markers, except for an attribute list at the end if the standard attr_list extension is enabled.

License

Copyright 2021 by Cris Luengo
Distributed under the MIT license (see LICENSE).

Based on:

• Extension logic, recognizing Markdown syntax:
  Arithmatex from PyMdown Extensions
  Copyright 2014 - 2017 Isaac Muse [e-mail]
  MIT license.

• Converting LaTeX into SVG:
  latex2svg.py
  Copyright 2017, Tino Wagner
  MIT license.

• Tweaking the output of latex2svg for embedding into HTML5, and use of cache:
  latex2svgextra.py from m.css
  Copyright 2017, 2018, 2019, 2020 Vladimír Vondruš [e-mail]
  MIT license.