Does anyone know of any DSLs or similar that are specific to graph/chart drawing? I.e. a language that defines a function from data to image, specialised toward visualising data? If not, what’s the closest thing? E.g. is there a JS chart-drawing library with an API that feels close to a DSL?

https://vega.github.io/ and https://vega.github.io/vega-lite/ count?

vega has json-schemas for its configs, but those are huge https://vega.github.io/schema/vega-lite/v4.json so if you fancy some clojure, I got draft lib https://github.com/akovantsev/json-schema-to-clojure-spec specifically to explore those schemas in repl (I don't remember if it handled schemas of such size though :))

vega, plot, ggplot, all based off "grammar of graphics" which defines a conceptual toolbox for data -> pixel space.

Graphviz and Penrose are two graph DSLs that are quite different from Vega.

I've done a thing some time ago that may be relevant: https://compostjs.github.io/compost/ It is fairly small composable DSL for composing visualizations - unlike grammar of graphics libraries (vega), it is more low-level and you construct graphical primitives yourself - but it handles mapping of units from "domain units" to pixels (where domain units can be continuous or categorical) - so the idea is to have something that is a sweet spot between low level drawing and high-level (Vega, D3, etc) libraries...

Thank you, Vega does look pretty close to what I’m describing, if one considers that giant JSON schemas like this are standing in for what could probably be a nice and tidy special-purpose language. I will investigate further.

schemas are "grammar of a language", not a "message written in a language".