Early last year, I posted a solution to this same question on the now inactive Google Groups forum. The idea is to use a
ui_template node to push the array of data points into the 3-rd party Plot.ly graphing library, and use its internal methods to convert the image into a jpg or png data buffer. Somewhat interesting reading, but limited in its scope, since the graph has to be visible in the dashboard in order to grab the image.
I've also had some luck grabbing images of svg graphs using the
save-svg-as-png library found on npm. The main issue with this approach is that support for css inherited fonts is missing (not sure if that is an issue with the current chartjs dashboard rendering). And I don't know how well it supports canvas-based graphs (which the dashboard appears to use).
If you still need to grab some graphs as images, I can see about digging up some code to elaborate on these two techniques. But generally, an interactive graph based on a db query is a far better user experience. Incidentally, when you mentioned "Crestron", is this for a presentation management system or something? I've been managing one of those for years, and would love to discuss ideas for integrating node-red...