Skip to content

Latest commit

 

History

History
87 lines (59 loc) · 5.22 KB

README.md

File metadata and controls

87 lines (59 loc) · 5.22 KB
Raw

Convert MathML to Latex

Introduction

This project provides a Python script to convert MathML into Latex.

Usage

./mathml2latex input.md output.md

Example input.md:

Gradient

Let <!--[if mathML]><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>f</mml:mi><mml:mo>:</mml:mo><mml:msup><mml:mi>ℝ</mml:mi><mml:mi>n</mml:mi></mml:msup><mml:mo>→</mml:mo><mml:mi>ℝ</mml:mi></mml:math><![endif]--> be a scalar field. The gradient is

  <!--[if mathML]><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="block"><mml:mo>∇</mml:mo><mml:mi>f</mml:mi><mml:mfenced><mml:mi>x</mml:mi></mml:mfenced><mml:mo>=</mml:mo><mml:mfenced open="[" close="]"><mml:mrow><mml:mtable><mml:mtr><mml:mtd><mml:maligngroup/><mml:mfrac><mml:mrow><mml:mo>&#120597;</mml:mo><mml:mi>f</mml:mi></mml:mrow><mml:mrow><mml:mo>&#120597;</mml:mo><mml:msub><mml:mi>x</mml:mi><mml:mn>1</mml:mn></mml:msub></mml:mrow></mml:mfrac></mml:mtd></mml:mtr><mml:mtr><mml:mtd><mml:maligngroup/><mml:mo>⋮</mml:mo></mml:mtd></mml:mtr><mml:mtr><mml:mtd><mml:maligngroup/><mml:mfrac><mml:mrow><mml:mo>&#120597;</mml:mo><mml:mi>f</mml:mi></mml:mrow><mml:mrow><mml:mo>&#120597;</mml:mo><mml:msub><mml:mi>x</mml:mi><mml:mi>n</mml:mi></mml:msub></mml:mrow></mml:mfrac></mml:mtd></mml:mtr></mml:mtable></mml:mrow></mml:mfenced></mml:math><![endif]-->

Example output.md:

Gradient
Let $f:{\mathbb{R}}^{n}\to \mathbb{R}$ be a scalar field. The gradient is
  $$\nabla f\left(x\right)=\left[\begin{array}{c}\frac{\mathit{\partial}f}{\mathit{\partial}{x}_{1}}\\ \vdots \\ \frac{\mathit{\partial}f}{\mathit{\partial}{x}_{n}}\end{array}\right]$$

output.md rendered as:

Rendered Latex Math

Background

I started this little project when attempting to migrate from OneNote to Markdown. I have a large number of math notes with heavy equations, which makes my journey much bumpier.

In OneNote, equations are stored in MathML format; while in Markdown, equations are in the form of Latex.

As this may help others in similar situations, I decided to jot down the approaches to convert OneNote to Markdown below.

There exist at least three ways to do the conversion.

  1. OneNote --> Word --> Markdown This method appears to be the most popular. I found several similar repos on Github. There are two steps in this approach:
    • Step 1: Export OneNote documents in Word format, i.e. .docx
      • This export function is supported in the standalone version of OneNote on Windows. I have not found it available on Mac or on the version installed from the Microsoft Store.
    • Step 2: Convert Word documents to Markdown with Pandoc
      • This approach has the advantage of being able to export all OneNote documents with a single PowerShell script.
      • However, it is a disaster for my equations. When exporting to .docx, all equations are converted into images, which not only breaks the line alignment but also loses the capability of editing equations in the future.

  1. OneNote --> HTML --> Markdown This approach is based on the one2html project which utilizes the onenote.rs parser.

    The converted equations are in the HTML format, rather than the image format. However, the converter does not support MathML which renders the converted equation garbled.


  1. OneMark --> Markdown (with MathML) --> Markdown (with Latex) OneMark is a great plugin that enables writing OneNote with Markdown syntax. It also comes with a handy function to export OneNote into Markdown. This approach consists of two steps:
    • Step 1: Export OneNote to Markdown with OneMark
      • Since OneMark only has Windows version, you need to do this on a Windows machine with the standalone version of OneNote.
      • One inefficiency here is that OneMark currently only supports exporting one page at a time. Thus it may be laborious if you have a large number of notes like me.
    • Step 2: Convert MathML to Latex in Markdown
      • Equations in the Markdown generated by OneMark are in form of MathML which is not edit-friendly and cannot be displayed in many Markdown editors.
      • To convert MathML to Latex, I write a Python script which results in this repo.

Mechanism

mathml2latex.py detects MathML blocks denoted by <!--[if mathML]> ... <![endif]-->. This wrapper block is generated by OneMark.

The conversion of a MathML block is conducted in two phases:

  1. Invoke XSLT MathML library to transform MathML structures to Latex markups

  1. Convert UTF characters to Latex markups
    • XSLT MathML only converts the math structures to Latex markups while leaving UTF symbols like π in the literal form.
    • Many Markdown editors fail to recognize these UTF symbols which results in a failure of rendering.
    • Thus, unicode2latex() utilizes a lookup table to convert these UTF symbols to Latex markups, e.g. \pi

Related

  • mathconverter : a nice math converter that inspires this project. Unfortunately it is not Markdown friendly.