Halftone QR — a picture inside a QR code

Text or link to encode

Picture

Drop an image here or choose a file
Faces and bold shapes with strong contrast work best

Image adjustments

Contrast

Brightness

Zoom

Dithering

Module grid

Invert picture QR code

Reference marks Pick the QR mask that best matches the picture

Dark Light

Checking whether the code scans…

Version–

Modules–

Picture area–

Mask–

PNG size

How it works

A scanner locates the code with the three corner squares, builds a grid, and reads one sample near the centre of each module. Everything else in a module is free. So each module is divided into a small grid (6×6 by default). The centre cells get the QR bit, and the other cells, 89% of the area with the default grid, get a dithered black-and-white version of your picture. High error correction absorbs the occasional misread.

This is the technique Erik and Martin Demaine describe for their QR prints (erikdemaine.org/prints/QR); its best-known academic treatment is Chu, Chang, Lee & Mitra, “Halftone QR Codes”, ACM Transactions on Graphics, 2013.

Tips: short text gives a smaller code with bigger modules, which scans more easily. Raise the contrast for soft photos. Always test the final file with a phone before printing it.