My gut goes to having an internal web server that ingests the data and renders the image.
Xpression can then link to that image.
For creating the image, the way I would do it is write a script that creates a SVG version of the chart. That would be easy because it is text.
Then use "Image Magik" to turn the SVG into a png.
https://imagemagick.org/
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Azathoth
Son of Cthulhu
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