Exporting UV distortion?

I would like to use UV distortion-- primarily size, not angle-- to modulate some bump mapping. Is there a way to export a distortion view from the UV editor?

I would prefer black and white. If I can’t get black and white, and am, say, stuck using a screenshot, is there a good way to transform the colorized code to a black and white version?

Also interested in other ways of doing this, like if there’s a node somewhere I don’t know about that would let me access UV density, like delta UV / delta worldPos.

There is a rgb to bw node that will convert a color to black and white.