ReSmush.it
Photo optimization

Capture web pages as images through a public HTTP API.
Screenshot Studio API is a free Photography API that requires no API key, is served over HTTPS and does not support CORS, so it should be called from a server.
Endpoints, schemas, rate limits, and error codes for the public Screenshot Studio API.
Details from screenshot-studio.com.

Unified API suite · now live
Geocode an address, validate an email, track a flight or pull stock data with one account, one dashboard and one API key.
Photo optimization
Stock Photos and Videos
The Screenshot Studio API is provided by Screenshot Studio (screenshot-studio.com). Endpoints, schemas, rate limits, and error codes for the public Screenshot Studio API.
Yes. The Screenshot Studio API is listed in the Photography category of the public-apis directory, which only includes APIs that are free or have a free tier. Check its documentation for rate limits and paid plans.
No. The Screenshot Studio API requires no authentication, so you can start making requests without signing up.
Not directly. The Screenshot Studio API does not allow CORS, so call it from a server, serverless function or proxy instead of front-end JavaScript.
Yes. The Screenshot Studio API is served over HTTPS, so it's safe to use in production.