Facebook, which was the use case you mentioned upthread, doesn't store 5MB images. You'd have to design for way less than 5MB, I should imagine.

That was kind of my point, was it not? QR Code might or might not have too much redundancy (depending on how resilient you want to be against what amount of sharing), but the general principle stands.

Lossy compression removes information by design, you want to keep all bits of information, therefore you have to represent your information in a redundant (and therefore inefficient, by density) way.