Open Source Ecosystems

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 comes with an option for offline conversion (which closely imitates GitHubs behavior), and 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, advanced image caching and optimization, host-ready file- and image-placement, pdf-conversion, emoji shortcode support, TOC support 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.

Here is a (not necessarily extensive) list of its advantages and features:

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. This is especially useful since it reflects GitHub's behavior to serve cached copies of README-images instead of linking to them directly, reducing tracking and possibly downscaling overlarge images in the process.
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. gh-md-to-html uses
LaTeX and dvisvgm if they are both installed (advantage: fast,
requires no internet), and otherwise the Codecogs EqnEditor (advantage: doesn't require
you to install 3 GB of LaTeX libraries) to achieve this.
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 as well as the browser extension). This is especially relevant considering that DarkReader doesn't usually
shift the colors of svg images, and the formulas added by gh-md-to-html's formula support are embedded as inline svg.
gh-md-to-html ensured that the formulas are the same color as the text, shifted in accordance with DarkReader's
current/enabled colorscheme.
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).
Allows you to choose a width for the box surrounding the text; this can increase readability if you intend to host the
markdown file stand-alone rather than embedded into a different html file (see
#25 and
Wikipedia).
Comes with an optional support for the use of [[_TOC_]], {:toc} and [toc] at the beginning of an otherwise empty
line to create a table of content for the document, like GitLab-flavored markdown does, among others.
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 RGBA to RGB, 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 equal 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.
Comes with an option to closely imitate GitHub's markdown-to-html-conversion behavior offline!
Emoji shortcode support.
Probably even more than that - this list here is no longer maintained, refer to the documentation further down this README for all options.

In case you are looking for an alternative to Pandoc for converting markdown to PDF, here is a list of reasons why you could want to use gh-md-to-html instead of Pandoc for the job:

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 this 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 gh-md-to-html if you are on Windows.

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

python3 -m pip install gh-md-to-html[pdf_export]

and install wkhtmltopdf (v0.12.6 or greater) to get the optional pdf-conversion feature and convert markdown files to pdf, and/or

python3 -m pip install gh-md-to-html[offline_conversion]

to get the optional offline-conversion feature up and running.

If you are on Windows, you might have to add wkhtmltopdf to your path in your current working directory in order to get pdf conversion to work, e.g. with PATH=%PATH%;c:/program files/wkhtmltopdf/bin or something similar, depending on your installation location.

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.

If you only want to imitate the conversion results yield by GitHub's REST API offline, but don't want image caching, formula support and fancy CSS styling, use

html_as_a_string = gh_md_to_html.core_converter.markdown(your_markdown_as_a_string)

in Python.

Documentation

Usage: gh-md-to-html <input_name> <optional_arguments>
Default behavior: By default, gh-md-to-html takes a markdown file name as an argument, and saves the generated HTMl in a file of the same name, with .html instead of .md. Some quirks:
- The generated CSS is stored in github-markdown-css/github-css.css (add -c to make it inline instead).
- All referenced images are cached, stored & referenced in ./images (add -i to disable this).
- All image & css links assume that you want to host the html file with your current directory as the root directory (add -w if you want to directly view it in a browser instead).
- All ids and file-internal links are prefaced by user-content-, so you can embed the generated html in a bigger website without risking ID clashes.
Some common use cases: Through past issues, I realised that there are some very common use cases that most people seem to have for this module. Here are the most common ones, and which options and arguments to use for them:
- preview a GitHub README: use -i -w --math false --box-width 25cm, though grip might be more efficient for this purpose.
- preview a GitLab README: see above, and add --toc to support GitLab's TOC syntax.
- as an alternative to pandoc-flavored markdown: use --math true --emoji-support 0 --dont-make-images-links true.
- having everything in one file: use -i -c to have everything in one file.
Converting markdown files from the web with --origin-type: You might want to not only convert a local markdown file, but also a file from a GitHub repository, a web-hosted one, or the contents of a string. Simply downloading these or storing them in a file is often not enough, since their location on the web also influences how the links to images they reference must be resolved. Luckily, gh-md-to-html has got your back! There is a number of different arguments you can use to describe what kind of file the input you gave references:
- --origin-type file: The default; takes a (relative or absolute) file path
- --origin-type repo: Takes a pth to a markdown file in a github repository, in the format <user_name>/<repo_name>/<branch-name>/<path_to_markdown>.md.
- --origin-type web: Takes the url of a web-hosted markdown file.
- --origin-type string: Takes a string containing markdown.
  Some of these options you use influences how image links within the markdown file are resolved; a later section of this README outlines this in detail.
Fine-tuning what goes where: gh-md-to-html is written with the goal of generating a host-ready static website for you, with your current working directory as its root. Aside from using -w to disable this and allow you to view the generated file directly in a browser, there are a number of options that allow you to fine-tune what goes where, and most popularly, change the root of the website. There is no need to do so unless you want to for some reason, so don't bother reading this if you don't need to!
- --website-root(or -w): Leaving this option empty, as discussed above, allows you to preview the generated html file directly in a browser (on most systems by double-clicking it) in case you don't want to host the generated html file, but you can also supply any directory that you want to use as the website's root to this. It defaults to your current working directory.
- --destination (or -d): The path, relative to --website-root, in which the generated html file is stored. By default, the website root is used for this.
- --image-paths (or -i): You can leave this empty to disable image caching, as described above (though this won't work in case you modified --origin-type), or supply a path relative to website-root to modify where images are stored. It defaults to images.
  Image caching makes sure that two pixel-identical images are stored in the same file location, to minimize loading time for files with multiple identical images.
  The image-paths-directory isn't automatically emptied between multiple runs of gh-md-to-html for this reason, to ensure that this optimization can be used cross-file when converting multiple files in a bulk.
- --css-paths (or -c): You can leave this empty to disable storing the CSS in an external CSS file (useful e.g. if you want to convert only one file), as described above, or supply a path relative to website-root to modify where the CSS file (called github-css.css) will be stored.
  The default is github-markdown-css.
- --output-name (or -n): The file name under which to store the generated html file in the destination-directory.
  You can use <name> anywhere in this string, and it will automatically be replaced with the name of the markdown file, so, for example, gh-md-to-html inp.md -n "<name>-conv.html" will store the result in ino-conv.html (this doesn't work with --origin-type string, of course).
  You can also use -n print in order to simply write the output to STDOUT (print it on the console) instead of saving it anywhere.
  The default value is <name>.html, so it adapts to your input file name.
- --output-pdf (or -p): The file in which to store the generated pdf.
  You can use the <name>-syntax here as well. If the -p-option isn't used, no pdf will be generated (and you need to have followed the pdfkit & wkhtmltopdf installation instructions above to have this option work), but you can use -p without any arguments to have it use <name>.pdf as a sensitive file name default.
exporting as pdf: As mentioned above, you can export the generated HTML file as a pdf using the --output-pdf-option. Doing so requires you to have wkhtmltopdf installed (the Qt-patched version), to add it to the PATH (if you are on Windows), and to have pdfkit installed (e.g. via pip3 install gh-md-to-html[offline_conversion]), but all of these requirements are already outlined above in the installation section. There are some things worth noting here, though. First of all, DO NOT use this option if you have valuable information in a file called {yourpdfexportdestination}.html, where {yourpdfexportdestination} is what you supplied to -p, since this file will be temporarily overwritten in the process; furthermore, do not use -p at all if you are supplying untrusted input to the -x-option. There are also some options specifically tailored for use with -p; these are currently:
- --style-pdf (or -s): Set this to false to disable styling the generated PDF file with GitHub's CSS. You might want to do this because the border that GitHub's CSS draws around the page can look counterintuitive in PDFs, though doing so can also negatively influence the appearance of other parts, so use this with a grain of salt.
changing which core markdown converter to use: gh-md-to-html doesn't actually do all that much heavy lifting itself when it comes to parsing markdown and converting it to PDF; instead, it wraps around a so-called "core converter" that does the basic conversion according to the markdown spec, and builds its own options, features, customizations and styling on top of that. By default, the GitHub markdown REST API is used for that, since it comes closest to what GitHub does with its READMEs, but you can also give gh-md-to-html any other basic markdown converter to work with.

gh-md-to-html also comes with two build-in alternative core converters to use, that imitate GitHub's REST API as close as possible whilst adding their own personal touch to it.

Option to decide the core converter:
- --core-converter (or -o): You can use this option to choose from a number of pre-defined core converters (see below) in case you want to differ from the default one.
  
  You can also supply a bash command (on UNIX/Linux systems) to this, or a cmd.exe command on Windows, in which {md} stands as a placeholder for where the shell-escaped input markdown will be inserted by gh-md-to-html. For example, gh-md-to-html inp.md -o "pandoc -f markdown -t html <<< {md}" will use pandoc as its core converter. You can also do so using multiple commands, like gh-md-to-html -o "printf {md} >> temp.md; pandoc -f markdown -t html temp.md; rm temp.md", as long as the result is printed to stdout.
  
  If you use the Python-interface to gh-md-to-html, you can also supply any function that converts a markdown string into a html string to this argument.
Pre-defined core converters that you can easily supply to --core-converter as strings:
- OFFLINE: Imitates GitHub's markdown REST API, but offline using mistune. This requires the optional dependencies for "offline_conversion" to be satisfied, by using pip3 install gh-md-to-html[offline_conversion] or pip3 install mistune>=2.0.0rc1.
- OFFLINE+: Behaves identical to OFFLINE, but it doesn't remove potentially harmful content like javascript and css like the GitHub REST API usually does. DO NOT USE THIS FEATURE unless you need a way to convert secure manually-checked markdown files without having all your inline js/styling stripped away!
support for inline-formulas: gh-md-to-html supports, by default, inline formulas (no matter which core converter, see above, you use). This means that you can write a LaTeX formula between two dollar signs on the same line, and it will be replaced with an SVG image displaying said formula. For example, $e = m \cdot c^2$ will add Einstein's famous formula as a svg image, well-aligned with the rest of the text surrounding it, into your document.

gh-md-to-html always tries to use your local LaTeX installation to do this conversion (advantage: fast and doesn't require internet). However, if LaTeX or dvisvgm are not installed or it can't find them, it uses an online converter (advantage: doesn't require you to install 3 GB of LaTeX libraries) to achieve this.

You can use the following options to modify this behavior:
- --math (or -m): Set this to false to disable formula rendering.
- --suppress-online-fallbacks: Set this to true to disable the online fallback for formula rendering, raising an error if its requirements aren't locally installed or can't be found for some reason.
image caching and image compression: As explained in-depth above, gh-md-to-html saves images so they can all be loaden from the same folder. This comes with the advantages of
- potentially reducing tracking (in case the images where hosted on a 3rd-party website)
- reducing the number of DNS lookups required to show your generated HTMl file (in case the images where hosted on different 3rd-party websites)
- reducing the number of images to load (if one or multiple md files you intend to host or view as html files contain the same or pixel-identical images)
In addition to these advantages, gh-md-to-html also allows you to set a level of image compression to use for these images. If you decide to do so, every image will be converted to JPEG (using a background color and quality settings of your liking), and images will be downscaled if the generated html states that they won't be needed at their full size anyways (you can make use of this e.g. by using <img>-tags directly in your document and supplying them with an explicit width or height value).

gh-md-to-html is also the only markdown converter capable of making use of the html srcset-attribute, which allows the generated document to reference several differently scaled versions of the same image, of whom the browser will then load the smallest large-enough one on smaller screen sizes, leading to great load reductions e.g. on mobile. Enabling this feature can lead to further loading time reductions without sacrificing any visible image quality, which makes gh-md-to-html the best choice if you want to generate fast-loading websites from your image-heavy markdown files.

The option to use for all of this is
- --compress-images. and it accepts a piece of JSON data with the following attributes:
  - 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.
    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 before reducing the quality.
  If this argument is left empty, no compression is used at all. If this argument is set to True, all default values are used. If it is set to json data and some values are omitted, the defaults ones are used for these.
  
  You can also pass a dict instead of a string containing JSON data if you are using this option in the Python frontend.
  
  Image compression won't work, for obvious reasons, if you use -i to disable image caching.
my personal choices: GitHub-flavored markdown and markdown in general makes some unpopular choices, and gh-md-to-html, imitating it, also makes a lot of these. If your goal isn't to be as close as possible to (github-flavored) markdown, and you want to utilize the full power that gh-md-to-html offers to the fullest, I recommend the following (very opinionated) list of settings and options. Note that some of these aren't safe when converting user-generated content, though.
- --math true: This is already enabled by default, so not really a recommendation, but you'll most likely want to have LaTeX math support in your file.
- --core-converter OFFLINE+: This converts the markdown files offline instead of using GitHub's REST API, and allows the use of unsafe things like inline code and every html you could wish for in your markdown file.
- --compress-images: There are many ways to finetune this options, but it allows for some great optimizations on the cached images, including the use of the HTML srcset-attribute, which no other markdown converter currently supports afaik.
- --box-width 25cm: You'll most likely want to limit the width of the box in which the generated website's content is displayed for reasons of readability, unless you plan to embed the generated html into a bigger html file.
- --toc true: This allows you to use [[_TOC_]] as a shortcut for a table of contents in the generated file.
- --dont-make-images-links true: By default, GitHub wraps every image into a link to the image source, unless the image is already wrapped into a different link. This option disables this behavior for more control over your image's links.
- --emoji-support 2: gh-md-to-html supports using emoji shortcodes, like :joy:, which are then replaced with emojis in the generated html file. --emoji-support 2 takes this one level further this by allowing you to use your own custom emojis, so :path/to/funny_image.png: will add funny_image.png as an emoji-sized emoji into the text.
- --soft-wrap-in-code-boxes true: By default, GitHub displays its multiline code boxes with a horizontal scrollbar if they are at a risk of overflowing. Use this option to have (imho more reasonable) soft-wrap in code boxes instead.

Please note that the options are listed ordered by relevance, and all of them have sensible defaults, so don't feel overwhelmed by how many there are; you can just read through them until you find what you where looking for, and safely ignore the rest. Most of the options are meant to customize default behavior, so none of them are mandatory for most use cases.

{help}

More detail on image caching paths:

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:

	`https://` or `http://`	abs. filepath	rel. filepath	starting with `/` (e.g. `/imagedir/image.png`)	not starting with `/` (e.g. `imagedir/image.png`)
`-t file`	from the address	abs. filepath	rel. filepath (from where the `.md`-file lies)	-	-
`-t string`	from the address	abs.filepath, but needs confirmation for security reasons	rel. filepath (to where the tool is called from), but needs confirmation for security reasons	-	-
`username/repo/dir/file.md -t repo`	from the address	-	-	`username/repo/imagedir/image.png`	`username/repo/dir/imagedir/image.png`
`https://foo.com/bar/baz.md -t web`	from the address	-	-	`https://foo.com/image.png`	`https://foo.com/bar/image.png`

Feedback

As with all of my projects, feedback (even if it is just something small like telling me your use case for my project, or telling me that you didn't like the README's structure, or telling me that you specifically liked one specific feature) is much appreciated, and helps me make this project better, even if it's something very tiny! You can just drop an issue with your feedback, short and non-formal, or even email me if you don't want to raise an issue for some reason. I do not plan on adding features in the future at the moment, but I am always open to fixing and tweaking existing features, documentation et cetera, and I would obviously love to hear your feature suggestions even if I do not plan on adding them in the near future.

Me supporting you & You supporting me

I am generally very responsive when it comes to GitHub issues, and I take them very serious and try to solve them ASAP. If you run into bugs, weird behaviors, installation errors and the like whilst using my tool, don't hesitate to tell me in an issue, so I can fix the problem!

If you found this tool useful, please consider starring it on GitHub to show me your appreciation! I would also appreciate if you told me about issues you encountered even if you managed to fix them in your own copy of the code, so I can fix them in this repo, too.

Attribution

The icons were made by

.md-file.icon: Freepik from flaticon.com
.md-file.icon: Freepik from flaticon.com
arrow-icon: Font Awesome by Dave Gandy, licensed under Creative Commons Attribution-Share Alike 3.0 Unported
GitHub-icon: GitHub icon on Iconscout

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.

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