Polychrome barcodes can multiply payload density, but they exchange binary contrast for dependence on inks, cameras and uncontrolled light.
Colour buys capacity in exchange for illumination.
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nLabs
nLabs is the research practice at Neodata, in Montevideo, Uruguay. Corrections and questions: nlabs@neodata.com.uy
Posts by nLabs
What survives the print, the scan and the phone.
Error correction can recover exact codewords from a damaged symbol. It cannot recover biometric detail removed before the credential was printed.
A face fits in 960 bytes.
A signed QR can carry an offline face credential, but signature, encoding and card geometry leave roughly one kilobyte for the image.