It can't, but it'd probably only be a few hours work to add. We'd just need to plug the rendering library we're using into an image encoder rather than a windowing library. There might also be some extra work required to do tiling if you wanted a screenshot that is the full height of the HTML page (bigger than will fit in a single GPU texture), but I can't imagine that would be too hard.

That’d be an amazing extension with lots of potential to mix up the existing Screenshot aaS business. I’m no Rust dev, so I can’t help here, but I’ll follow the project closely!

Given general css support is not complete, would you really want a screenshot of something that might look radically different on a commonly used browser?

I guess perhaps such functionality will be more useful when the CSS support is more complete?

I added an example of rendering to image today. It's a bit rough atm (not very configurable), but it seems reasonably fast.

Many websites don't render properly anymore without Javascript. A pure "html + css renderer" would probably be of limited utility for screenshotting.

You can use Playwright with Webkit, which is much lighter weight than Chrome.

You might also look into trying Prince XML.

Its happy path is typesetting via HTML/CSS, but it may fit your use case as well.