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https://github.com/yagarea/jektex

A Jekyll plugin for fast server-side cached LaTeX rendering, with support for macros. Enjoy the comfort of LaTeX and Markdown without cluttering your site with bloated JavaScript.
https://github.com/yagarea/jektex

bundle bundler gem hacktoberfest jekyll jekyll-plugin katex katex-plugin katex-support kramdown latex markdown nojavascript nojs ruby-gem static-site static-site-generator static-website tex yaml

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A Jekyll plugin for fast server-side cached LaTeX rendering, with support for macros. Enjoy the comfort of LaTeX and Markdown without cluttering your site with bloated JavaScript.

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README 

        
[![Gem Version](https://badge.fury.io/rb/jektex.svg)](https://rubygems.org/gems/jektex)



# ![Jektex](https://blackblog.cz/assets/img/projects/jektex.svg)

A Jekyll plugin for blazing-fast server-side cached LaTeX rendering, with support for macros.

Enjoy the comfort of LaTeX and Markdown without cluttering your site with bloated JavaScript.

This project is [endorsed by KaTeX.org](https://katex.org/docs/libs#jekyll).



## Features

- Renders LaTeX formulas during Jekyll rendering

- Works without any client-side JavaScript

- Is faster than any other server-side Jekyll LaTeX renderer

- Supports user-defined global macros

- Has I/O-efficient caching system

- Dynamically informs about the number of expressions during rendering

- Is very easy to setup

- Doesn't interfere with Jekyll workflow and project structure

- Marks invalid expressions in document, printing its location during rendering

- Is highly configurable with sensible defaults

- Makes sure that cache does not contain expression rendered with outdated configuration

- Supports two major LaTeX notations



## Usage

Jektex supports both the built-in Kramdown math notation, and the newer LaTeX-only math notation.



### Kramdown notation

**Inline formula**  

Put formula between two pairs of dollar signs (`$$`) inside of paragraph.

```latex

Lorem ipsum dolor sit amet, consectetur $$e^{i\theta}=\cos(\theta)+i\sin(\theta)$$

adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.

```



**Display formula**  

Put formula between two pairs of dollar signs (`$$`) and surround it with two empty lines.

```latex

Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor

incididunt ut labore et dolore magna aliqua.



$$ \left[ \frac{-\hbar^2}{2\mu}\nabla^2 + V(\mathbf{r},t)\right] \Psi(\mathbf{r},t) $$



Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex

ea commodo consequat.

```



_Why Jektex does not use conventional single `$` for inline formulas and double `$$` for

display mode?  

This is how [kramdown](https://kramdown.gettalong.org/) (Jekyll's markdown parser) works 

so I decided to respect this convention. It makes this plugin more consistent and universal.

See [this issue](https://github.com/gettalong/kramdown/issues/762) for more context._



### LaTex math mode notation

**Inline formula**  

Put formula between two escaped brackets `\(` `\)`.

Its position in the text does not matter.

```latex

Lorem ipsum dolor sit amet, consectetur \(e^{i\theta}=\cos(\theta)+i\sin(\theta)\)

adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.

```



**Display formula**  

Put formula between two escaped square brackets `\[` `\]`.

Its position in the text does not matter.

```latex

Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor

incididunt ut labore et dolore magna aliqua.



\[ \left[ \frac{-\hbar^2}{2\mu}\nabla^2 + V(\mathbf{r},t)\right] \Psi(\mathbf{r},t) \]



Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex

ea commodo consequat.

```



### Logo macro

There is a build in macro for jektex logo. You can use it as `\jektex`.



### Config

Jektex si highly configurable via your `_config.yml` file.



**Disabling cache**  

You can disable caching with `disable_disk_cache = true` in `_config.yml`.

Caching is enabled by default.

You can find more information on [Jekyll's official website](https://jekyllrb.com/docs/configuration/options/).



**Setting cache location**  

By default, Jektex cache will be saved in `.jekyll-cache` directory.

This results in its deletion when you call `jekyll clean`.

To prevent cache deletion or to change the cache location, you can specify `cache_dir` in `_config.yml`:

```yaml

jektex:

  cache_dir: ".jektex-cache"

```



**Ignoring files**  

By default, Jektex tries to render LaTeX in all files rendered by Jekyll.

This can sometimes be undesirable, for example when rendering an _RSS feed_ with excerpts containing LaTeX.

Jektex solves this by using the `ignore` option:

```yaml

jektex:

  ignore: ["*.xml", "README.md", "_drafts/*" ]

```



You can use conventional wild cards using `*`.

This example configuration ignores all `.xml` files, `README.md` and all files in the `_drafts` directory.



Another way to ignore specific posts is setting the `jektex` attribute in front matter to `false`:

```yaml

---

title: "How Jektex works"

category: "Development"

jektex: false

layout: post

---

```



Setting `jektex` tag to `true` or not setting at all will result in Jektex rendering LaTeX expressions in that post.



**Using macros**  

You can define global macros:

```yaml

jektex:

  macros:

    - ["\\Q", "\\mathbb{Q}"]

    - ["\\C", "\\mathbb{C}"]

```

And yes, you have to escape the backlash (`\`) with another backlash.

This is due to the [yaml specification](https://yaml.org/).



You can define macros with parameters:

```yaml

jektex:

  macros:

    - ["\\vec", "\\mathbf{#1}"]

    - ["\\addBar", "\\bar{#1}"]

```

This simulates behaviour of LaTeX `\newcommand`.



**Silencing Jektex output**  

Jektex periodically informs the user about rendered/cached equations.

If this is not desired, you can set the `silent` option (`false` by default).

```yaml

jektex:

  silent: true

```



**Complete examples**  

Recommended config:

```yaml

jektex:

  cache_dir: ".jektex-cache"

  ignore: ["*.xml"]

  silent: false

  macros:

    - ["\\Q", "\\mathbb{Q}"]

    - ["\\C", "\\mathbb{C}"]

```



Having no configuration is equivalent to this:

```yaml

jektex:

  cache_dir: ".jekyll-cache"

  ignore: []

  silent: false

  macros: []

```



## Installation

This plugin is available as a [RubyGem](https://rubygems.org/gems/jektex).



**Using bundler**  

Add Jektex to your `Gemfile`:

```ruby

group :jekyll_plugins do

    gem "jektex"

end

```



and run `bundle install`



**Without bundler**  

Run `gem install jektex`



**After installation**  

Add Jektex to your plugin list in your `_config.yml` file

```yaml

plugins:

    - jektex

```



and don't forget to add `katex.min.css` to you HTML head:

```html



```

It is much better practice to download the [**css** file](https://cdn.jsdelivr.net/npm/[email protected]/dist/katex.min.css) and load it as an asset from your server directly.

You can find more information on [KaTeX's website](https://katex.org/docs/browser.html).



## Contributions and bug reports

Feel free to report any bugs or even make feature request in [issues on official repository](https://github.com/yagarea/jektex/issues).

I am opened for pull requests as well.