You've seen QR codes with logos in the center. Maybe a Starbucks QR with their siren, or a brand's QR with their logo stamped dead center. How does that work? Doesn't putting a graphic in the middle of the code just... break it?
Short answer: yes, but QR codes are designed to survive it. Here's the mechanism.
Reed-Solomon error correction
QR codes use Reed-Solomon error correction, originally developed for CD scratch recovery. The spec defines four levels: L (7% damage), M (15%), Q (25%), and H (30%). At Level H, up to 30% of the code data can be damaged or obscured and the code still scans correctly.
When you embed a logo, you're deliberately obscuring part of the code. As long as the obscured area stays within the error correction budget, scanners reconstruct the missing data from the redundant bits elsewhere in the pattern.
