QR Code Generation in C++: QR-Code-generator Library

QR-Code-generator Library for C++: Complete Guide

QR codes have become an integral part of the modern digital world. They are used in advertising, logistics, payment systems, and even educational projects. If you are developing a C++ application and want to add QR code generation functionality, the QR-Code-generator library is a simple, lightweight, and efficient tool. In this article, we will thoroughly examine what this library is, how to install it, and provide working code examples.

What is QR-Code-generator?

QR-Code-generator is a cross-platform C++ library (also available in C, Python, Java) that allows you to create QR codes of various versions and error correction levels. Key advantages:

• No external dependencies (works out of the box).
• Supports all 40 QR code versions (from 21×21 to 177×177 modules).
• Error correction levels: L (7%), M (15%), Q (25%), H (30%).
• Output as a string (char*) or binary array.
• Support for Unicode (UTF-8) and numeric/alphanumeric modes.

The library is ideal for embedding in server applications, command-line utilities, or educational C++ projects.

Installation and Setup

Installation is extremely simple. You can download the source code from Nayuki's GitHub repository or use a package manager (e.g., vcpkg). Let's look at the manual method:

1. Download the files qrcodegen.hpp and qrcodegen.cpp.
2. Place them in your project folder.
3. Include the header file in your code: #include "qrcodegen.hpp".
4. Compile the project with the -std=c++11 flag or higher.

Example compilation using g++:

g++ -std=c++11 main.cpp qrcodegen.cpp -o qr_generator

Main API Functions

The library provides a minimalistic yet powerful API. Main functions:

• qrcodegen::QrCode::encodeText(text, ecl) — encodes a text string into a QR code with a specified error correction level.
• qrcodegen::QrCode::encodeBinary(data, ecl) — encodes binary data.
• getSize() — returns the size of the QR code (number of modules in width).
• getModule(x, y) — checks if a module (pixel) is set at coordinates (x, y).

Example 1: Generating a QR Code and Printing to Console

The simplest example — create a QR code for a text string and display it as ASCII art. This code is useful for debugging or terminal demonstrations.

#include <iostream>#include <string>#include "qrcodegen.hpp"

using namespace std;using namespace qrcodegen;

int main() {    // Create a QR code for text with error correction level H (30%)    const QrCode qr = QrCode::encodeText("https://pythonlib.ru", QrCode::Ecc::HIGH);        // Print the QR code to the console (█ characters and spaces)    for (int y = 0; y < qr.getSize(); y++) {        for (int x = 0; x < qr.getSize(); x++) {            cout << (qr.getModule(x, y) ? "██" : "  ");        }        cout << endl;    }    return 0;}

Result: The console will display a QR code that can be scanned by any smartphone. Level H provides maximum resistance to damage.

Example 2: Creating a QR Code with Binary Data

Sometimes you need to encode not text, but arbitrary bytes (e.g., serialized data). Use encodeBinary.

#include <vector>#include "qrcodegen.hpp"

using namespace qrcodegen;

int main() {    // Prepare binary data (byte array)    std::vector<uint8