I had a colleague (thanks Sanjay!) make a similar tool at a hackfest (you can see the source code here: https://github.com/FusionAuth/fusionauth-site/blob/master/sr... ).

I've modified it a bit to take a URL, but haven't yet set it up to read a config file to make a large number of screenshots easy to do.

We do outline certain fields or other areas in the doc to highlight a point. That's caused some hesitation on my part. However, it looks like I could use imagemagick to automatically put a red box or similar on an image (with a `-draw` command).

We have a ton of screenshots (600+) throughout our doco, and a way to initialize our product to a known state, so the pieces are all there.

One of these days it'll be worthwhile to do this.