libqrencode `libqrencode/`

Type: QR Code Generation Library
License: LGPL-2.1-or-later
Fork Origin: GitHub
Status: Detached Fork (independently maintained)
Standards: ISO/IEC 18004:2015 Latest Version: 0.0.5-1

Overview

libqrencode is a fast and compact library for encoding data into a QR Code symbol. It supports the full range of QR Code functionality as defined by the ISO standard.

ProjT Launcher maintains a fork of libqrencode for controlled integration and monorepo CI compatibility.

Usage in ProjT Launcher

libqrencode is used for:

  • Account linking — Microsoft account QR authentication
  • Share URLs — Quick sharing of instance/mod links
  • Export/Import — Instance configuration sharing

Features

Feature Status
QR Code Model 1 & 2 ✅
Micro QR Code ✅
All error correction levels ✅
Structured append ✅
8-bit byte mode ✅
Kanji mode ✅
ECI mode ✅

Error Correction Levels

Level Recovery Use Case
L ~7% High density
M ~15% Standard (default)
Q ~25% Industrial
H ~30% Critical data

Build Instructions

Prerequisites

  • CMake 3.10+ or Autotools
  • C99 compiler (GCC, Clang, MSVC)
  • libpng (optional, for PNG output)

CMake Build

cd libqrencode
mkdir build && cd build
cmake .. -DCMAKE_BUILD_TYPE=Release
cmake --build .
ctest -V

Autotools Build

cd libqrencode
./autogen.sh
./configure
make
make check

CMake Options

Option Description Default
WITH_TOOLS Build qrencode CLI tool ON
WITH_PNG Enable PNG support ON
WITH_TESTS Build test suite ON
BUILD_SHARED_LIBS Build shared library ON

API Usage

Basic Example

#include <qrencode.h>
#include <stdio.h>

int main() {
    QRcode *qr = QRcode_encodeString("https://projecttick.org",
                                      0,                    // Version (0 = auto)
                                      QR_ECLEVEL_M,         // Error correction
                                      QR_MODE_8,            // Encoding mode
                                      1);                   // Case sensitive

    if (qr == NULL) {
        fprintf(stderr, "Failed to encode\n");
        return 1;
    }

    // Access the QR code data
    printf("Version: %d\n", qr->version);
    printf("Width: %d\n", qr->width);

    // qr->data contains the QR code matrix
    // Each byte: bit 0 = module (1=black, 0=white)

    QRcode_free(qr);
    return 0;
}

Structured Append (Large Data)

// Split data across multiple QR codes
QRcode_List *list = QRcode_encodeStringStructured(
    large_data, 0, QR_ECLEVEL_M, QR_MODE_8, 1);

for (QRcode_List *entry = list; entry != NULL; entry = entry->next) {
    // Process each QR code in sequence
    process_qrcode(entry->code);
}

QRcode_List_free(list);

Command Line Tool

The qrencode CLI tool creates QR code images:

# Generate PNG
qrencode -o output.png "Hello World"

# Generate SVG
qrencode -t SVG -o output.svg "https://projecttick.org"

# Generate ASCII art
qrencode -t ASCII "Hello World"

# Specify error correction level
qrencode -l H -o secure.png "Sensitive Data"

Output Formats

  • PNG (requires libpng)
  • EPS
  • SVG
  • ANSI terminal
  • ASCII art
  • UTF-8 terminal

Documentation

Resource Location
API Reference libqrencode/qrencode.h
Man Page libqrencode/qrencode.1.in
Original README Upstream library documentation

Testing

cd libqrencode/build
ctest -V

# Or with autotools
cd libqrencode
make check

See ci-libqrencode.yml for CI configuration.

Copyright & Licensing

Copyright (C) 2006-2017 Kentaro Fukuchi <kentaro@fukuchi.org>

This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.

Full license: libqrencode/COPYING

Related Documentation

External Links

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Last updated: February 19, 2026 Edit on GitHub