Re:The rise of the QR code in China
by smaili on Sunday May 28, 2017 @05:03PM
(#14436081)
Slightly off topic but one thing I never understood was how they're able to add additional art to their QR codes and still have phones successfully read and decrypt the code. Are there parts of the code that don't actually provde any value and can be replaced? Or do they use a modified protocol that enables them to use custom QR codes?
[ Parent
| on HN ]
See https://research.swtch.com/qart by Russ Cox
QR codes have error correction that can be set to four levels (http://www.qrcode.com/en/about/error_correction.html). If you set the level high enough, you can cover parts of the code and it will still be readable.
QR codes contain error correction bits. Depending on the error correction level up to 30% of the information can be restored. This allows you to add overlays that conceal some of the information while the code will still scan correctly.