[aniviacat]

It can pull images from a domain. That would be difficult (since for client-side rendered sites it would require loading the site in a sandboxed environment) or impossible (if the site actively prevents that using CORS or similar, or if it happens to include scripts which expect to be run in a normal environment).

[siamese_puff]

There is also the ability to run things like Playwright on the edge a la Cloudflare Workers. You can fallback to rendering JS required sites through that and do clientside imagemagick WASM shenanigans on the client once the worker returns direct links to all the images.

[jasonjmcghee]

Yup totally fair - would likely require you upload the images manually for pure client-side.

You might still be able to offset a portion of the compute by just figuring out the URLs of the images on the back-end, sending that list to the client, which would then download and do the optimization / resizing.