PrismLauncher/libraries/qt-qrcodegenerator/qr.cpp

#include "qr.h"
#include "qrcodegen.hpp"

void paintQR(QPainter& painter, const QSize sz, const QString& data, QColor fg)
{
    // NOTE: At this point you will use the API to get the encoding and format you want, instead of my hardcoded stuff:
    qrcodegen::QrCode qr = qrcodegen::QrCode::encodeText(data.toUtf8().constData(), qrcodegen::QrCode::Ecc::LOW);
    const int s = qr.getSize() > 0 ? qr.getSize() : 1;
    const double w = sz.width();
    const double h = sz.height();
    const double aspect = w / h;
    const double size = ((aspect > 1.0) ? h : w);
    const double scale = size / (s + 2);
    // NOTE: For performance reasons my implementation only draws the foreground parts in supplied color.
    // It expects background to be prepared already (in white or whatever is preferred).
    painter.setPen(Qt::NoPen);
    painter.setBrush(fg);
    for (int y = 0; y < s; y++) {
        for (int x = 0; x < s; x++) {
            const int color = qr.getModule(x, y);  // 0 for white, 1 for black
            if (0 != color) {
                const double rx1 = (x + 1) * scale, ry1 = (y + 1) * scale;
                QRectF r(rx1, ry1, scale, scale);
                painter.drawRects(&r, 1);
            }
        }
    }
}