Erich Blume 33463764d1 Add QArt Tuner: QR code art generator with interactive web UI

Single-file Go tool implementing the QArt technique (Russ Cox, 2012)
using only the public rsc.io/qr API. Generates QR codes whose data
modules form a recognizable image by exploiting error correction
freedom via GF(2) Gaussian elimination.

Includes a web UI with live-updating sliders for version, mask,
rotation, dx/dy offset, and scale. Keyboard shortcuts for rapid
iteration. Also works as a CLI for batch generation.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

2026-03-27 15:33:36 -07:00

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QArt Tuner

Generates QR codes whose data modules form a recognizable image, using the QArt technique by Russ Cox. Lives in utils/qart/.

Quick Reference

Item	Value
Source	`utils/qart/main.go`
Language	Go (managed via mise)
Dependency	rsc.io/qr (BSD 3-clause)
Launch web UI	`QART_IMAGE=photo.png mise run serve` (from `utils/qart/`)
CLI	`mise x go -- go run . -url URL -image IMG -out out.png`

How It Works

QR error correction (Reed-Solomon coding) allows some data and check bits to be freely chosen. The tool:

Builds a QR code plan for the given URL and version
Converts the source photo to a grayscale brightness grid at QR module resolution
For each ECC block, models the data/check bit relationships as a matrix over GF(2)
Uses Gaussian elimination to find which bits can be independently assigned
Assigns bits to match the target image brightness, prioritizing high-contrast areas

The result is a valid, scannable QR code whose black/white modules approximate the source image.

Web UI

The interactive tuner (-serve flag) provides sliders for all parameters with live preview.

Keyboard shortcuts: arrow keys (dx/dy offset), [/] (mask), -/= (version), r (rotate).

Parameters

Parameter	Range	Effect
version	1-8	QR density — higher = more modules = finer detail
mask	0-7	QR mask pattern — dramatically affects which pixels are controllable
dx/dy	-15 to 15	Shifts image relative to QR structure (avoids alignment dot on eyes)
rotation	0-3	Quarter turns
scale	1-16	Output pixels per QR module
dither	on/off	Floyd-Steinberg dithering

Credits

Technique: Russ Cox, QArt Codes (2012)
QR library: rsc.io/qr — QR layout, encoding, GF(256) arithmetic
Implementation: Claude Code (Opus 4.6) with direction from Erich Blume

mise-tasks — Task runner for BlumeOps operations

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