github-flavored-markdown-to-html

A user-friendly python-module and command-line frontend to convert markdown to html. It uses GitHubs online Markdown-to-html-API by default (which requires internet connection), but any other python- or commandline tool can be plugged into it as well. Whatever you use it with is automatically extended with a ton of functionality, like more in- and output options, github-flavored CSS, formula support, image downloading, host-ready file- and image-placement, pdf-conversion, and more.

Whilst its main purpose is the creation of static pages from markdown files, for example in conjunction with a static website builder or github actions if you host on Github, it can be very well-used for any other purpose.

Advantages include:

• Lets you specify the markdown to convert as a string, as a repository path, as a local file name or as a hyperlink.
• Pulls any images referenced in the markdown files from the web/ your local storage and places them in a directory relative to your specified website root, so the resulting file structure is host-ready for static sites. Multiple arguments allow the customization of the saving locations, but the images will always be referenced correctly in the resulting html files.
• Creates all links as root-relative hyperlinks and lets you specify the root directory as well as the locations for css and images, but uses smart standard values for everything.
• Supports inline LaTeX-formulas (use $-formula-$ to use them), which GitHub usually doesn't (this is done using the Codecogs EqnEditor).
• Supports exporting to pdf with or without Github styling, using the pdfkit python module (if it is installed).
• Tested and optimized to look good when using Darkreader (the .js-module, not necessarily the browser extension. This means that formulas are displayed with a light text when in darkmode, amongst other things).
• Supports umlauts and other non-ascii-characters in plain text as well as in multiline code blocks, which the github REST api usually doesn't.
• Allows you to choose which tool or module to use at its core for the basic markdown to html conversion.
• Styles its output with github's README-css (can be turned off).
• Comes with an option to compress and downscale all images referenced in the markdown file (does not affect the original images) with a specified background color (default is white) for converting RGB to RGBA, and a specified compression rate (default is 90). Images with a specified width or height attribute in pixels get scaled down to that size to reduce loading time. This helps severely reduce the size of generated pages for markdown files with lots of images. There is also an option to save all images in multiple sizes and let the html viewer/browser pick the one fitting for the viewport size (using the img srcset attribute), thus making gh-md-to-html the only md-to-html converter with builtin srcset support for image load reduction.
• If two images from equal or different sources are referenced in the given markdown file, and both would be saved in the same resolution et cetera, both are pointed to the same copy in the generated html to minimize loading overhead.

Whilst using pandoc to convert from markdown to pdf usually yields more beautiful results (pandoc uses LaTeX, after all), gh-md-to-html has its own set of advantages when it comes to quickly converting complex files for a homework assignment or other purposes where reliability weights more than beauty:

• pandoc converts .md to LaTeX and then renders it to pdf, which means that images embedded in the .md are shown where they fit best in the .pdf and not, as one would expect it from a .md-file, exactly where they were embedded.
• pandoc's pandoc-flavored markdown supports formulas; however, some specific rules apply regarding the amount of whitespace cornering the $-signs and what characters the formula may start with. These rules do not apply in some common markdown editors like MarkText, though, which leads to lots of frustration when formulas that worked in the editor don't work anymore when converting with pandoc (MarkText's own export-to-pdf-function sometimes fails on formula-heavy files without an error message, though, which makes it even less reliable). The worst part is that, whenever pandoc fails converting .md to .pdf because of this, it shows the line number of the error based on the intermediate .tex-file instead of the input .md-file, which makes it difficult to find the problem's root. As you might have guessed, gh-md-to-html couldn't care less about the amount of whitespace you start your formulas with, leaving the decision up to you.
• pandoc supports multiple markdown flavors. The sole formula-supporting one of these is pandoc-flavored markdown, which comes with some quite specific requirements regarding the amount of trailing whitespace before a sub-list in a nested list, and other requirements to create multi-line bullet point entries. These requirements are not fulfilled my many markdown-editors (such as MarkText) and not required by many other markdown flavors, causing pandoc to not render multiline bullet point entries and nestled lists correctly in many cases. gh-md-to-html, on the other hand, supports both nested lists like you would expect it, and formulas, releasing the burden of having to edit entire markdown files to make then work with pandoc's md-to-html-conversion from your shoulders.

To sum it up, pandoc's md-to-pdf-conversion acts quite unusual when it comes to images, nested lists, multiline bullet point entries, or formulas, and gh-md-to-html does not.

Installation

Use pip3 install gh-md-to-html to install directly from the python package index, or python3 -m pip install ... if you are on windows.

Or use

git clone https://github.com/phseiff/github-flavored-markdown-to-html.git
cd github-flavored-markdown-to-html
pip3 install .

to clone from master and add changes before installing.

Both might require sudo on Linux, and you can optionally do

sudo apt-get install wkhtmltopdf
python3 -m pip install pdfkit

(if you want to use the optional pdf features) to include pdf support into your installation.

Usage

If you want to access the interface with your command line, you can just supply gh-md-to-html with the arguments documented in the help text (accessible with gh-md-to-html -h and shown below). On windows, you must supply python3 -m gh_md_to_html with the corresponding arguments.

If you want to access the interface via python, you can use

import gh_md_to_html

and then use gh_md_to_html.main() with the same arguments (and default values) you would supply to the command line interface.

Documentation

All arguments and how they work are documented in the help text of the program, which looks like this:

usage: __main__.py [-h] [-t {file,repo,web,string}]
                   [-w WEBSITE_ROOT [WEBSITE_ROOT ...]]
                   [-d DESTINATION [DESTINATION ...]]
                   [-i IMAGE_PATHS [IMAGE_PATHS ...]]
                   [-c CSS_PATHS [CSS_PATHS ...]]
                   [-n OUTPUT_NAME [OUTPUT_NAME ...]]
                   [-p OUTPUT_PDF [OUTPUT_PDF ...]] [-s STYLE_PDF]
                   [-f FOOTER [FOOTER ...]] [-m MATH]
                   [-r FORMULAS_SUPPORTING_DARKREADER]
                   [-x EXTRA_CSS [EXTRA_CSS ...]]
                   [-o CORE_CONVERTER [CORE_CONVERTER ...]]
                   [-e COMPRESS_IMAGES [COMPRESS_IMAGES ...]]
                   MD-origin [MD-origin ...]

Convert markdown to HTML using the GitHub API and some additional tweaks with
python.

positional arguments:
  MD-origin             Where to find the markdown file that should be
                        converted to html

optional arguments:
  -h, --help            show this help message and exit
  -t {file,repo,web,string}, --origin-type {file,repo,web,string}
                        In what way the MD-origin-argument describes the origin
                        of the markdown file to use. Defaults to file. The
                        options mean: 
                        * file: takes a relative or absolute path to a file
                        * repo: takes a path to a markdown-file in a github
                        repository, such as <user_name>/<repo_name>/<branch-
                        name>/<path_to_markdown>.md 
                        * web: takes an url to a markdown file
                        * string: takes a string containing the files content
  -w WEBSITE_ROOT [WEBSITE_ROOT ...], --website-root WEBSITE_ROOT [WEBSITE_ROOT ...]
                        Only relevant if you are creating the html for a static
                        website which you manage using git or something similar.
                        --html-root is the directory from which you serve your
                        website (which is needed to correctly generate the links
                        within the generated html, such as the link pointing to
                        the css, since they are all root- relative), and can be
                        a relative as well as an absolute path. Defaults to the
                        directory you called this script from. If you intent to
                        view the html file on your laptop instead of hosting it
                        on a static site, website-root should be a dot and
                        destination not set. The reason the generated html files
                        use root-relative links to embed images is that on many
                        static websites, https://foo/bar/index.html can be
                        accessed via https://foo/bar, in which case relative
                        (non-root- relative) links in index.html will be
                        interpreted as relative to foo instead of bar, which can
                        cause images not to load.
  -d DESTINATION [DESTINATION ...], --destination DESTINATION [DESTINATION ...]
                        Where to store the generated html. This path is relative
                        to --website-root. Defaults to "".
  -i IMAGE_PATHS [IMAGE_PATHS ...], --image-paths IMAGE_PATHS [IMAGE_PATHS ...]
                        Where to store the images needed or generated for the
                        html. This path is relative to website-root. Defaults to
                        the "images"-folder within the destination folder.
  -c CSS_PATHS [CSS_PATHS ...], --css-paths CSS_PATHS [CSS_PATHS ...]
                        Where to store the css needed for the html (as a path
                        relative to the website root). Defaults to the
                        "<WEBSITE_ROOT>/github-markdown-css"-folder.
  -n OUTPUT_NAME [OUTPUT_NAME ...], --output-name OUTPUT_NAME [OUTPUT_NAME ...]
                        What the generated html file should be called like. Use
                        <name> within the value to refer to the name of the
                        markdown file that is being converted (if you don't use
                        "-t string"). You can use '-n print' to print the file
                        (if using the command line interface) or return it (if
                        using the python module), both without saving it.
                        Default is '<name>.html'.
  -p OUTPUT_PDF [OUTPUT_PDF ...], --output-pdf OUTPUT_PDF [OUTPUT_PDF ...]
                        If set, the file will also be saved as a pdf file in the
                        same directory as the html file, using pdfkit, a python
                        library which will also need to be installed for this to
                        work. You may use the <name> variable in this value like
                        you did in --output-name.
  -s STYLE_PDF, --style-pdf STYLE_PDF
                        If set to false, the generated pdf (only relevant if you
                        use --output-pdf) will not be styled using github's css.
  -f FOOTER [FOOTER ...], --footer FOOTER [FOOTER ...]
                        An optional piece of html which will be included as a
                        footer where the 'hosted with <3 by github'-footer
                        usually is. Defaults to None, meaning that the section
                        usually containing said footer will be omitted
                        altogether.
  -m MATH, --math MATH  If set to True, which is the default, LaTeX-formulas
                        using $formula$-notation will be rendered.
  -r FORMULAS_SUPPORTING_DARKREADER, --formulas-supporting-darkreader FORMULAS_SUPPORTING_DARKREADER
                        If set to true, formulas will be shown light if the
                        darkreader .js library is included in the html and the
                        user prefers darkmode. This is checked by looking for a
                        script embedded from a src ending with "darkreader.js"
                        and by checking the prefers-color- scheme option in the
                        browser. You can also supply any other script src to
                        look for. Please note that this won't have any effect
                        unless you inject the darkreader .js library into the
                        generated html; doing so is not included in this module.
  -x EXTRA_CSS [EXTRA_CSS ...], --extra-css EXTRA_CSS [EXTRA_CSS ...]
                        A path to a file containing additional css to embed into
                        the final html, as an absolute path or relative to the
                        working directory. This file should contain css between
                        two <style>-tags, so it is actually a html file, and can
                        contain javascript as well. It's worth mentioning and
                        might be useful for your css/js that every element of
                        the generated html is a child element of an element with
                        id xxx, where xxx is "article-" plus the filename
                        (without extension) of: 
                        * output- name, if output-name is not "print" and not
                        the default value.
                        * the input markdown file, if output- name is "print",
                        and the input type is not string. * the file with the
                        extra-css otherwise. If none of these cases applies, no
                        id is given.
  -o CORE_CONVERTER [CORE_CONVERTER ...], --core-converter CORE_CONVERTER [CORE_CONVERTER ...]
                        The converter to use to convert the given markdown to
                        html, before additional modifications such as formula
                        support and image downloading are applied; this can be
                        * on Unix/ any system with a cmd: a command containing
                        the string "{md}", where "{md}" will be replaced with an
                        escaped version of the markdown file's content, and
                        which returns the finished html. Please note that
                        commands for Unix-system won't work on Windows systems,
                        and vice versa etc. 
                        * when using gh-md-to- html in python: A callable which
                        converts markdown to html, or a string as described
                        above.
  -e COMPRESS_IMAGES [COMPRESS_IMAGES ...], --compress-images COMPRESS_IMAGES [COMPRESS_IMAGES ...]
                        Reduces load time of the generated html by saving all
                        images referenced by the given markdown file as jpeg.
                        This argument takes a piece of json data containing the
                        following information; if it is not used, no compression
                        is done: 
                        * bg-color: the color to use as a background color when
                        converting RGBA-images to jpeg (an RGB-format). Defaults
                        to "white" and accepts almost any HTML5 color-value
                        ("#FFFFFF", "#ffffff", "white" and "rgb(255, 255, 255)"
                        would've all been valid values).
                        * progressive: Save images as progressive jpegs. Default
                        is False. 
                        * srcset: Save differently scaled versions of the image
                        and provide them to the image in its srcset attribute.
                        Defaults to False. Takes an array of different widths or
                        True, which serves as a shortcut for "[500, 800, 1200,
                        1500, 1800, 2000]".
                        * quality: a value from 0 to 100 describing at which
                        quality the images should be saved (this is done after
                        they are scaled down, if they are scaled down at all).
                        Defaults to 90. If a specific size is specified for a
                        specific image in the html, the image is always
                        converted to the right size. If this argument is left
                        empty, no compression is down at all. If this argument
                        is set to True, all default values are used. If it is
                        set to json data and values are omitted, the defaults
                        are also used. If a dict is passed instead of json data
                        (when using the tool as a python module), the dict is
                        used as the result of the json data.

As mentioned above, any image referenced in the markdown file is stored locally and referenced using a root-relative hyperlinks in the generated html. How the converter guesses the location of the image is shown in the following table, with the type of imagelink noted on the top and the type of input markdown noted on the left:

Demonstration

I added the following demonstration, whose files where created from the root directory of this projects directory, which relates to the root directory of the site I am hosting them on:

I also did the following demonstrations for automated image downloading, who where all successful (Note that they where run from the parent directory of my repository and that instructions on how to run them can be found within the test files themselves. Also note that the test not only shows that images are stored and embedded correctly, but also that images from different files using the same name stored within the same image directory don't overwrite each other.):

I also added a $formula$ here ($\sum_{i\ge e^2}^{7.3}\frac{4}{5}$) to demonstrate the formula rendering (which you won't see when viewing this README directly on github since, like I said, github usually doesn't support it.)

A directory listing of these example outputs- and inputs can be found here.

Some Notes

In case you are not happy with the margin left and right of the text, you can manually adjust it by modifying the margin-values hardcoded in prototype.html in this repository. An other thing to note is that, even though gh-md-to-html supports multi line formulas, you may still use one (one!) dollar sign per line without it triggering a formula, since every formula requires two of these. However, if you use two single dollar signs in two different columns of the same row off a table, your table will break. In the end, you are always better off properly escaping dollar signs, even though we give you the freedom not to do so on one occasion per line!

When embedding images from disk (not via an url), you should ensure that the path you load the image from does not contain whitespaces. Otherwise, the markdown code to embed the image will be shown like any other text within the resulting html/pdf instead of being replaced with an image. I will eventually get to change this; if you want this to be done ASAP, feel free to drop a comment under the corresponding issue, and I will get to work on it ASAP.

Known Usages

This tool is already used by

• myself (for homework assignments in pdf-format four times a week, so you can rest assured that yes, the person maintaining it is also using it themselves)
• feel free to drop an issue if you want to be included in this list!

DISCLAIMER: This module is neither written by Github, nor is it endorsed with Github, supported by Github, powered by Github or affiliated with Github. It only uses a public API provided by Github as well as a .css-file licensed by Github under the MIT license.