Graphoid should also be able to render graph images by accepting a graph specification JSON, instead of a reference to an existing graph. For example:

https;//graphoid.wikimedia.org/en.wikipedia.org/render/png
POST parameters:
    graphspec: { ... }

The domain is needed to properly resolve local URLs, e.g. /wiki/Article?action=raw => https://en.wikipedia.org/wiki/Article?action=raw

Additionally, there should be another service

https;//graphoid.wikimedia.org/en.wikipedia.org/hash

With the same POST parameter that simply returns the hash value instead of an image. The hash value will be generated by hashing a combined graph definition + all external data sources. The hash value will not depend on the output format of the image (png/svg/...)