Asciidoctor Mathematical

Asciidoctor Mathematical is an Asciidoctor extension that provides an alternate solution for converting STEM expressions in an AsciiDoc document into a displayable format. It has the benefit of working across all converters.

The library is called Asciidoctor Mathematical because it relies on the Mathematical library to parse and transform (aka render) LaTeX expressions. It also uses the AsciiMath library to convert AsciiMath notation to LaTeX so Mathematical can process it.

This page explains how Asciidoctor Mathematical works, how to install it and activate it, and where to go to learn more information about it.

How it works

The library works by visiting each STEM node in the parsed document and converting it to an image, effectively replacing the STEM node with an image node. This takes the burden of transforming the STEM expressions off of the converter. All the converter sees are image nodes that reference the generated images.

Upon visiting each STEM node, the extension first extracts the expression source. If the expression is written in AsciiMath, the extension uses the AsciiMath library to convert that expression to LaTeX. The extension then passes the expression to Mathematical to render it as an image. The image is sized automatically to accommodate the rendered expression and, if necessary, resized to fit within the line. Once the image is generated, the extension replaces the STEM node in the parsed document with an image node that references the generated image.

When the extension finishes processing all the STEM nodes, it unsets the stem attribute on the document to indicate no further STEM processing should be performed on the document.

Benefits and drawbacks

Since Asciidoctor Mathematical replaces all STEM nodes with image nodes, it serves as an all-purpose solution for STEM processing. All converters know how do deal with image nodes. The extension can be used with the built-in converters as well as add-on converters such as PDF and EPUB3.

The main drawback of Asciidoctor Mathematical when compared to MathJax is that you don’t have a lot of control over the size and resolution of the images it generates. It also lacks the interactivity with the expression that MathJax provides. So when you’re converting to HTML, MathJax is going to give you a better result.

Another drawback when compared to MathJax is that it requires installing an extra library, and that library can be difficult to install. Nonetheless, if you need it and you’re up for the challenge, that’s where we’re headed next.


Asciidoctor Mathematical is distributed as a gem named asciidoctor-mathematical. You can install it using the Ruby packaging tools (gem or bundle).

$ gem install asciidoctor-mathematical

However, you may run into difficulty installing this gem. Asciidoctor Mathematical depends on Mathematical, which is a native gem. In other words, Mathematical must be recompiled during installation, which requires access to build tools and native development libraries on the host system. Furthermore, this compilation currently only works on Linux. You cannot install this gem on Windows. Please refer to the installation section in the Asciidoctor Mathematical documentation to learn which system tools and development libraries you need in order to install it.

If you run into problems installing this gem, or need to use it on Windows, consider using the Asciidoctor Docker container. The Asciidoctor Docker container launches with the asciidoctor-mathematical gem preinstalled.


Once Asciidoctor Mathematical is installed, you can activate the extension when invoking Asciidoctor using the -r flag:

$ asciidoctor -r asciidoctor-mathematical stem-sample.adoc

If you’re invoking Asciidoctor via the API, you must require the gem before invoking Asciidoctor:

require 'asciidoctor-mathematical'

Asciidoctor.convert_file 'stem-sample.adoc', safe: :safe

When the extension is activated, it will automatically find STEM nodes in the parsed document and replace them with images.

Improve image resolution

To get the best quality output and maximize speed of conversion, you should configure Asciidoctor Mathematical to generate SVG files. You control this setting using the mathematical-format AsciiDoc attribute as follows:

$ asciidoctor -r asciidoctor-mathematical -a mathematical-format=svg stem-sample.adoc

The extension will now generate SVG images instead of PNG images.

More info

To learn more about how to use this extension and the options it provides, see the project’s README.