@mnair,
CanvasJS is a JavaScript library that render charts on the client-side. To expose API for downloading chart, you will have to run it in a headless browser & serve the captured screenshot on request. Please take a look at this sample project which uses puppeteer to save the image in the sever side.
If this doesn’t fulfill your requirement, kindly brief us further about your requirement or an example so that we can understand your scenario better and help you out.
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Manoj Mohan
Team CanvasJS
