Yomu

Pure Dart QR Code & Barcode Reader Library

Yomu is a zero-dependency pure Dart implementation of a QR code and barcode reader library. It works in any Dart environment including Flutter, Dart CLI applications, and server-side Dart.

✨ Why Yomu?

• 📦 Zero Dependencies: No external package dependencies. Keep your app's dependency graph clean.
• 🎯 Pure Dart: No C++/Native code. Works instantly on Web (Wasm/JS), Desktop, and Mobile without build issues.
• 🚀 High Performance: Full HD in ~4.4ms, 4K in ~9ms on M4 MacBook Air (AOT). Fast enough for real-time scanning.
• 🛡️ Robust & Tested: Comprehensive test coverage. Tested against hundreds of distorted, noisy, and unevenly lit images.

🚀 Quick Start

QR Code + All Barcodes

import 'package:yomu/yomu.dart';

void main() {
  // Create a YomuImage container
  final image = YomuImage.rgba(
    bytes: imageBytes,
    width: 300,
    height: 300,
  );

  // Decode QR codes and all barcode formats
  final result = Yomu.all.decode(image);
  print('Decoded: ${result.text}');
}

QR Code Only

// For QR code only scanning
final result = Yomu.qrOnly.decode(YomuImage.rgba(
  bytes: imageBytes,
  width: width,
  height: height,
));

📖 API Reference

Yomu Class

The main entry point class.

Constructor / Static	Description
Yomu.all	QR codes + all barcode formats
Yomu.qrOnly	QR codes only
Yomu.barcodeOnly	1D barcodes only
Yomu.realtime	All formats, tryHarder off (per-frame scanning)
Yomu({enableQRCode, barcodeScanner})	Custom configuration

Method	Description
decode()	Decode the first QR code or barcode in an image
decodeAll()	Detect and decode all QR codes in an image

Detection vs Latency (tryHarder)

decode() runs escalating retry strategies by default (tryHarder: true) when the fast path fails: corner grid search, despeckle, tolerant finder and a full-resolution retry. This significantly improves the detection rate for noisy, dirty, perspective-distorted and small codes, while successful scans pay nothing. decodeAll() applies the same strategy to multi-code sheets: detected-but-undecodable codes get the corner rescue, and a pass that finds nothing escalates to despeckle and full resolution.

The retries only cost time on images that fail the fast path (roughly +8ms on a Full HD frame without a code, AOT). Pick by use case:

• Single images (photos, uploaded pictures): keep the default. A slower failure is better than a missed code.
• Real-time camera streams: use Yomu.realtime (or tryHarder: false). Frames without a code fail as fast as possible; a code missed on one frame is caught on a later one.

YomuImage Class

A platform-agnostic container for image data.

Factory	Description
YomuImage.rgba()	Create from RGBA bytes (4 bytes/pixel)
YomuImage.bgra()	Create from BGRA bytes (4 bytes/pixel)
YomuImage.grayscale()	Create from grayscale bytes (1 byte/pixel)
YomuImage.yuv420()	Create from Y-plane of YUV420 camera image

🔧 Support Status

Supported Image Classes

Yomu targets modern capture sources: printed codes, on-screen codes, and ordinary camera scans. Instead of relying on era-specific photo corpora, the test fixtures are generated to bracket the capability boundary of each distortion axis from both sides (see scripts/generate_stress_qr.py):

Distortion axis	Decodes	Does not decode
Salt & pepper noise	25%	30%
Low-light (Gaussian) noise	σ=110	σ=120
Gray dirt occlusion	30%	35%
Gaussian blur	radius 5.0	radius 6.0
Perspective (top squeeze)	0.3	0.4
Perspective (side squeeze)	0.6	— (saturates)
JPEG artifacts	quality 1	— (no boundary)
Specular glare	full saturation	— (EC absorbs it)
Screen moire	amplitude 0.7	amplitude 0.8
Composite casual scan¹	blur 5.0	blur 5.5

¹ Mild perspective (0.2) + lighting gradient + blur. Each component alone is well inside its single-axis boundary.

Degradations outside these definable classes — arbitrary surface curvature, finder patterns cut out of the frame, damage beyond the error-correction capacity — are out of scope; that long tail is the domain of ML-based detectors.

Encoding Modes (QR)

Mode	Support
Numeric	✅
Alphanumeric	✅
Byte (Latin-1/UTF-8)	✅
Kanji	✅
ECI	❌ Not Supported

1D Barcode Support

Format	Support	Description
EAN-13	✅	International retail (includes JAN)
EAN-8	✅	Small products
UPC-A	✅	North American retail
Code 128	✅	Logistics, high-density
Code 39	✅	Industrial, alphanumeric
ITF	✅	Interleaved 2 of 5, logistics
Codabar	✅	Libraries, blood banks

🎯 Performance

Run the benchmark suite:

uv run scripts/benchmark_runner.py

Standard Images (≤1000px)

• Environment: M4 MacBook Air (2024), AOT Compiled

Mode	Avg Decode Time
AOT	~0.92ms
JIT	~1.30ms

Large Images (Fused Downsampling)

Images >1MP are automatically processed with a fused conversion step for optimal performance.

Resolution	Avg Decode Time
4K (3840×2160)	~9.0ms
Full HD (1920×1080)	~4.4ms

License

MIT License - see LICENSE for details.