Graphoid (git repo) is a node.js service that converts a graph definition into a static PNG image using the same Vega library code that runs in advanced browsers. Graphoid is used as a fallback for non-JS enabled/compatible browsers - wikitech.wikimedia.org 
The service is available on the Wikimedia cluster at graphoid.wikimedia.org - mediawiki.org
You can install it yourself:
git clone https://gerrit.wikimedia.org/r/mediawiki/services/graphoid cd graphoid npm install npm start
The service URLs contain the domain of the page (for example mediawiki.org), service version (v1), the title of the page with the graph (PageTitle), revision ID of the page (12345, but could be 0 for current), and a hash ID of the graph itself (also used in HTML page to identify graph definition), for example:
# See also:
* Extension:Graph documentation - mediawiki.org
* Vega documentation - github
Vega is a visualization grammar, a declarative format for creating, saving and sharing interactive visualization designs.
The MediaWiki web API is a web service that provides convenient access to wiki features, data, and meta-data over HTTP. - mediawiki.org