A Jekyll plugin to convert diagram descriptions into images using Kroki

Add the jekyll-kroki Gem to the :jekyll_plugins group of your site's Gemfile:

group :jekyll_plugins do
  gem "jekyll-kroki"
end

Kroki supports over 20 popular diagram languages spanning several dozen diagram types. The examples page provides a taste of what's possible.

In Markdown, simply write your diagram description inside a fenced code block with the language specified:

```plantuml
participant Jekyll
participant Kroki #MediumSpringGreen

Jekyll -> Kroki: Encoded diagram description
Kroki --> Jekyll: Rendered diagram in SVG format
```

When Jekyll builds your site, the jekyll-kroki plugin will encode the diagram, send it to the Kroki server for rendering, then replace the diagram description in the generated HTML with the rendered diagram in SVG format:

The site remains truly static as the SVG is directly embedded in the HTML files that Jekyll serves. Jekyll only depends on the Kroki server (which can also be run locally) during the build stage, and all of the client-side processing that is normally used to render diagrams into images is eliminated.

jekyll-kroki uses the same Markdown fenced code syntax as the GitLab Kroki integration, allowing diagram descriptions in Markdown files to be displayed seamlessly in both the GitLab UI and on GitLab Pages sites generated using Jekyll.

You can specify the URL of the Kroki instance to use in the Jekyll _config.yml file:

kroki:
  url: "https://my-kroki.server"

This is useful if you want to run a Kroki instance locally or your organisation maintains its own private Kroki server. jekyll-kroki will use the public Kroki instance https://kroki.io by default if a URL is not specified.

Embedding diagrams as SVGs directly within HTML files can be dangerous. You should only use a Kroki instance that you trust (or run your own!). For additional security, you can configure a Content Security Policy (CSP) using custom Webrick headers in the Jekyll _config.yml file:

webrick:
  headers:
    Content-Security-Policy: "Add a policy here"

Bug reports and pull requests are welcome! For major changes, please open an issue first to discuss what you would like to change.