qrc — QR code encoder for MoonBit

Qrc encodes your data into QR codes. It has built-in QR matrix renderers for SVG, ANSI terminal and text.

This is a MoonBit port of the original OCaml qrc library by Daniel Bünzli.

Features

• ✅ QR code encoding with multiple data modes (numeric, alphanumeric, byte)
• ✅ Automatic mode detection
• ✅ Multiple output formats: SVG, ANSI terminal, plain text, compact text
• ✅ Reed-Solomon error correction with Galois Field arithmetic
• ✅ No external dependencies
• ✅ WebAssembly compatible
• ⚠️ Kanji mode (treated as byte mode)

Installation

moon install bobzhang/qrc

Usage

Basic Usage

///|
test {
  // Generate a QR code with default settings
  let qr = @bobzhang/qrc.encode("Hello, MoonBit!")

  // Print QR code information
  println(@bobzhang/qrc/render.info(qr))

  // Render as text
  println(@bobzhang/qrc/render.to_text(qr))

  // Render as compact text (using Unicode block characters)
  println(@bobzhang/qrc/render.to_compact_text(qr))

  // Render as SVG
  let svg = @bobzhang/qrc/render.to_svg(qr)
  println(svg)

  // Render as ANSI terminal output (with colors)
  println(@bobzhang/qrc/render.to_ansi(qr))
}

Advanced Usage

///|
test {
  // Generate QR code with specific error correction level
  let qr = @qrc.encode_with_ec("Important data", H)

  // Manual mode detection
  let mode = @qrc.detect_mode("12345") // Returns Mode::Numeric
  let mode2 = @qrc.detect_mode("HELLO WORLD") // Returns Mode::Alphanumeric
  let mode3 = @qrc.detect_mode("Hello, World!")
  // Returns Mode::Byte
}

Data Modes

The library automatically detects the best encoding mode:

• Numeric: Only digits 0-9 (most efficient for numbers)
• Alphanumeric: Digits, uppercase letters A-Z, and symbols $%*+-./:
• Byte: Any data (UTF-8 encoded)
• Kanji: Japanese characters (currently treated as byte mode)

Error Correction Levels

• L: ~7% correction capability
• M: ~15% correction capability (default)
• Q: ~25% correction capability
• H: ~30% correction capability

Example Output

QR Code Information:
Version: 1
Size: 21x21
Mode: Byte
Error Correction: M (~15%)
Data: "Hello, MoonBit!"

Text representation:
██████████████  ████  ██████████████
██          ██  ████  ██          ██
██  ██████  ██  ████  ██  ██████  ██
██  ██████  ██  ████  ██  ██████  ██
██  ██████  ██  ████  ██  ██████  ██
██          ██  ████  ██          ██
██████████████  ████  ██████████████
                ████                
████████████████████████████████████
...

API Reference

Core Functions

• encode(data: String) -> QRCode - Generate QR code with default error correction
• encode_with_ec(data: String, ec: ErrorCorrectionLevel) -> QRCode - Generate QR code with specific error correction
• detect_mode(data: String) -> Mode - Detect the best encoding mode for data

Rendering Functions

• @render.to_text(qr: QRCode) -> String - Plain text representation
• @render.to_compact_text(qr: QRCode) -> String - Compact Unicode representation
• @render.to_svg(qr: QRCode) -> String - SVG format
• @render.to_ansi(qr: QRCode) -> String - ANSI terminal with colors
• @render.info(qr: QRCode) -> String - QR code information

Running the Example

# Clone the repository
git clone <repository-url>
cd qrc

# Run tests
moon test

# Run the example
moon run src

Limitations

This is a functional implementation demonstrating MoonBit capabilities:

• ✅ Full Reed-Solomon error correction with proper Galois Field arithmetic
• ✅ Supports all error correction levels (L, M, Q, H)
• ✅ Proper data formatting with mode indicators and padding
• ✅ QR version 1 (21x21 modules) with finder patterns and timing patterns
• ⚠️ Kanji mode is treated as byte mode
• ⚠️ No format information or version information encoding
• ⚠️ No masking patterns applied

The Reed-Solomon implementation includes:

• Complete GF(256) Galois Field arithmetic
• Generator polynomial computation
• Proper error correction codeword generation
• Data capacity management for different error correction levels

For production use with higher versions and advanced features, consider extending this implementation.

Contributing

This project demonstrates porting OCaml code to MoonBit. Contributions to improve the implementation are welcome!

License

ISC License - same as the original OCaml library.

Acknowledgments

• Original OCaml qrc library by Daniel Bünzli
• MoonBit language team for the excellent tooling and documentation