simonw/shot-scraper has a number of cli args, a GitHub actions repo template, and docs: https://shot-scraper.datasette.io/en/stable/

From https://news.ycombinator.com/item?id=30681242 :

> Awesome Visual Regression Testing > lists quite a few tools and online services: https://github.com/mojoaxel/awesome-regression-testing

> "visual-regression": https://github.com/topics/visual-regression