Here's an interesting read on the Reference Image feature in Apple's new iPhones:

https://security.apple.com/blog/apple-reference-image/

tl;dr the image sensor in the phone effectively boots into a secure mode, creates a "secure digital negative", cryptographically signs it (using Secure Enclave) and preserves the metadata throughout any subsequent image manipulation.

At the same time, it preserves privacy/anonymity by not allowing the image to be linked to individual phones.