History

Project Nayuki 8329a7108f Slightly simplified the calculation of alignment pattern spacing in a non-obvious way, adapted from David Evans's "Lean QR" project.		3 months ago
..
Makefile	Removed the test worker program in every language and the Python batch tester, because this is not core functionality and is hard to explain.	3 years ago
Readme.markdown	- In the project (top-level) readme file, kept one language's code example and moved all others out to language-specific readme files.	3 years ago
qrcodegen-demo.c	Added null checks and error termination logic to runnable main C code after calls to malloc()/calloc(), removed an unnecessary non-null assertion.	3 years ago
qrcodegen-test.c	Renamed a C library internal function getModule() to getModuleBounded().	3 years ago
qrcodegen.c	Slightly simplified the calculation of alignment pattern spacing in a non-obvious way, adapted from David Evans's "Lean QR" project.	3 months ago
qrcodegen.h	Rewrote comments for top-level QR-encoding functions in C, to correspond better to other language ports.	3 years ago

Readme.markdown

QR Code generator library - C

Introduction

This project aims to be the best, clearest QR Code generator library. The primary goals are flexible options and absolute correctness. Secondary goals are compact implementation size and good documentation comments.

Home page with live JavaScript demo, extensive descriptions, and competitor comparisons: https://www.nayuki.io/page/qr-code-generator-library

Features

Core features:

Significantly shorter code but more documentation comments compared to competing libraries
Supports encoding all 40 versions (sizes) and all 4 error correction levels, as per the QR Code Model 2 standard
Output format: Raw modules/pixels of the QR symbol
Detects finder-like penalty patterns more accurately than other implementations
Encodes numeric and special-alphanumeric text in less space than general text
Completely avoids heap allocation (malloc()), instead relying on suitably sized buffers from the caller and fixed-size stack allocations
Coded carefully to prevent memory corruption, integer overflow, platform-dependent inconsistencies, and undefined behavior; tested rigorously to confirm safety
Open-source code under the permissive MIT License

Manual parameters:

User can specify minimum and maximum version numbers allowed, then library will automatically choose smallest version in the range that fits the data
User can specify mask pattern manually, otherwise library will automatically evaluate all 8 masks and select the optimal one
User can specify absolute error correction level, or allow the library to boost it if it doesn't increase the version number
User can create a list of data segments manually and add ECI segments

More information about QR Code technology and this library's design can be found on the project home page.

Examples

#include <stdbool.h>
#include <stdint.h>
#include "qrcodegen.h"

// Text data
uint8_t qr0[qrcodegen_BUFFER_LEN_MAX];
uint8_t tempBuffer[qrcodegen_BUFFER_LEN_MAX];
bool ok = qrcodegen_encodeText("Hello, world!",
    tempBuffer, qr0, qrcodegen_Ecc_MEDIUM,
    qrcodegen_VERSION_MIN, qrcodegen_VERSION_MAX,
    qrcodegen_Mask_AUTO, true);
if (!ok)
    return;

int size = qrcodegen_getSize(qr0);
for (int y = 0; y < size; y++) {
    for (int x = 0; x < size; x++) {
        (... paint qrcodegen_getModule(qr0, x, y) ...)
    }
}

// Binary data
uint8_t dataAndTemp[qrcodegen_BUFFER_LEN_FOR_VERSION(7)]
    = {0xE3, 0x81, 0x82};
uint8_t qr1[qrcodegen_BUFFER_LEN_FOR_VERSION(7)];
ok = qrcodegen_encodeBinary(dataAndTemp, 3, qr1,
    qrcodegen_Ecc_HIGH, 2, 7, qrcodegen_Mask_4, false);

More complete set of examples: https://github.com/nayuki/QR-Code-generator/blob/master/c/qrcodegen-demo.c .