Qt QR Code Generator Library

Qt QR Code Generator is a simple C++ class that uses the qrcodegen library to generate QR codes from QStrings in Qt applications. It can also split large payloads into animated QR codes and export them as looping GIFs.

Usage

1. Copy the Qt-QrCodeGenerator folder in your lib folder.
2. Include the Qt-QrCodeGenerator project include (pri) file using the include() qmake function.
3. Use the QrCodeGenerator class in your code:

#include <QrCodeGenerator>

QrCodeGenerator generator;
QString data = "https://www.example.com";
QImage qrCodeImage = generator.generateQr(data);

4. That's all! Check the example project as a reference for your project if needed.

Here are the steps to run the example using cmake (specific steps for LINUX ONLY):

cd ./example
mkdir -p build
cd build
cmake ../
make
./qrexample # runs executable

Animated QR codes

For payloads too large to fit (or scan reliably) in a single QR code, the library can split the data across several frames that are displayed in sequence. The simplest way is to ask for an animated GIF and let QMovie handle playback:

#include <QrCodeGenerator>
#include <QBuffer>
#include <QMovie>

QrCodeGenerator generator;
QByteArray data = ...; // large payload, QString also supported

// 512 bytes per frame, 250 ms per frame -> looping GIF89a
QByteArray gif = generator.generateGifQr(data, 512, 250);

auto *buffer = new QBuffer(this);
buffer->setData(gif);
buffer->open(QIODevice::ReadOnly);
auto *movie = new QMovie(buffer, "gif", this);
label->setMovie(movie);
movie->start();

// ...or save it to disk
QFile file("qr.gif");
file.open(QFile::WriteOnly);
file.write(gif);

If you need access to the individual frames (custom rendering, your own timer, etc.), use generateAnimatedQr() instead:

AnimatedQrCode animated = generator.generateAnimatedQr(data, 512, 250);

int count = animated.frameCount();   // number of frames
QImage frame = animated.frame(0);    // frame images, all the same size
int delay = animated.frameDuration(); // suggested ms per frame
animated.saveGif("qr.gif");          // same GIF encoder as generateGifQr()

Frame protocol

Each frame is a QR code (binary mode) containing:

"{index}/{total}|" + chunk

• index is the 1-based frame number, total the number of frames.
• chunk is a contiguous slice of the original payload, at most chunkSize bytes long. Concatenating the chunks of frames 1..total yields the original payload.

This is the same format used by AnimatedQRCodeReader, so frames produced by this library can be decoded by that reader. Error detection within each frame is provided by the QR code's own error correction; the header lets a reader detect missing or duplicated frames and reassemble out of order.

License

This project is licensed under the MIT License. See the LICENSE file for details.