Cloudflare isn’t a traditional CDN with its own path or subdomain. All site traffic routes through Cloudflare by default.
If Google hits your site via Cloudflare, it may or may not pull a cached version, depending on:
How long you have Edge Cache TTL set
How popular that image is (more popular files stay in cache longer)
Which Cloudflare POP Google hits (every POP is like its own separate CDN)
As a user, the only way to tell if the image was pulled from Cache or not is to look at the response headers for HIT/MISS/etc. The only way to tell if Google hit the cache is…you really can’t because it won’t show up in logs. You’d just know if it missed the cache if it’s in your server log.