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Render LaTeX within your Github Readmes

Project description

Renders LaTeX for Github Readmes

\begin{equation*} \huge\text{Hello \LaTeX} \end{equation*}

Make sure that pdflatex is installed.


readme2tex is a Python script that “texifies” your readme. It takes in Github Markdown and replaces anything enclosed between dollar signs with rendered \(\text{\LaTeX}\).

In addition, unlike the other Github TeX renderers, readme2tex ensures that inline mathematical expressions are properly aligned with the rest of the text to avoid giving a “jumpy” look to the document.

Examples:

Here’s a display level equation

\begin{equation*} \frac{n!}{k!(n-k)!} = {n \choose k} \end{equation*}

The code that was used to render this equation is just

$$
\frac{n!}{k!(n-k)!} = {n \choose k}
$$

Note: you can escape $ so that they don’t render.

Here’s an inline equation.

It is well known that if \(ax^2 + bx + c =0\), then \(x = \frac{-b \pm \sqrt{b^2- 4ac}}{2a}\).

The code that was used to render this is:

It is well know that if $ax^2 + bx + c = 0$, then $x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}$.

Notice that the equations line up with the baseline of the text, even when the height of these two images are different.

Sometimes, you might run into equations that are bottom-heavy, like \(x^2\sum\limits_{3^{n^{n^{n}}}}\). Here, readme2tex can compute the correct offset to align this equation to the baseline of your paragraph of text as well.

Installation

Currently, you just need to have readme2tex on your python-path, and you can call

Usage

python -m readme2tex --output README.md

It will then look for a file called readother.md and compile it down to a readable Github-ready document.

In addition, you can specify other arguments to render.py, such as:

  • --readme READOTHER.md The raw readme to process. Defaults to READOTHER.md.

  • --output README.md The processed readme.md file. Defaults to README_GH.md.

  • --packages ... A list of addition packages to use during \(\text{\LaTeX}\) compilation. This is optional.

  • --svgdir svgs/ The directory to store the output svgs. The default is svgs/

  • --branch master Experimental Which branch to store the svgs into, the default is just master.

  • --username username Your github username. This is optional, and render.py will try to infer this for you.

  • --project project The current github project. This is also optional.

  • --nocdn True Ticking this will use relative paths for the output images. Defaults to False.

  • --htmlize False Ticking this will output a X.md.html file so you can preview what the output looks like. Defaults to False.

  • --valign False Ticking this will use the valign trick (detailed below) instead. See the caveats section for tradeoffs.

Technical Tricks

How can you tell where the baseline of an image is?

By prepending every inline equation with an anchor. During post-processing, we can isolate the anchor, which is fixed at the baseline, and crop it out. It’s super clowny, but it does the job.

Caveats

Github does not allow you to pass in custom style attributes to your images. While this is useful for security purposes, it makes it incredibly difficult to ensure that images will align correctly to the text. readme2tex circumvents this using one of two tricks:

  1. In Chrome, the attribute valign=offset works for img tags as well. This allows us to shift the image directly. Unfortunately, this is not supported within any of the other major browsers, therefore this mode is not enabled by default.

  2. In every (reasonably modern) browser, the align=middle attribute will vertically center an image. However, the definition of the vertical “center” is different. In particular, for Chrome, Firefox, (and probably Safari), that center is the exact middle of the image. For IE and Edge however, the center is about 5 pixels (the height of a lower-case character) above the exact center. Since this looks great for non-IE browsers, and reasonably good on Edge, this is the default rendering method. The trick here is to pad either the top or the bottom of the image with extra spaces until the baseline of the equation is at the center. For most equations, this works great. However, if you have a tall equation, like \(\frac{~}{\sum\limits_{x^{x^{x^{x}}}}^{x^{x^{x^{x}}}} f(x)}\), you’ll notice that there might be a lot of slack vertical spacing between these lines. If this is a deal-breaker for you, you can always try the --valign True mode. For most inline equations, this is usually a non-issue.

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