class RetinaImageProvider : public QQuickImageProvider {
public:
    RetinaImageProvider()
      : QQuickImageProvider(QQuickImageProvider::Pixmap)
    {
    }

    virtual QPixmap requestPixmap(const QString &id, QSize *size, const QSize &requestedSize)
    {
#ifdef Q_OS_ANDROID
        QString localFile("assets:/qml/img/" + id);
#else
        QString localFile("qml/img/" + id);
#endif
        bool retina(false);
        if (qApp->devicePixelRatio() * QGuiApplication::primaryScreen()->geometry().height() > 768) {
            const int dotIndex = localFile.lastIndexOf(QLatin1Char('.'));
            if (dotIndex != -1) {
                QString retinaFile = localFile;
                retinaFile.insert(dotIndex, QStringLiteral("@2x"));
                if (QFile(retinaFile).exists()) {
                    localFile = retinaFile;
                    retina = true;
                }
            }
        }

        QPixmap pixmap(localFile);
        int width(pixmap.width());
        int height(pixmap.height());
        *size = QSize(width, height);
        if (requestedSize.width() > 0 || requestedSize.height() > 0) {
            pixmap = pixmap.scaled(QSize(
                requestedSize.width() > 0 ? requestedSize.width() : width,
                requestedSize.height() > 0 ? requestedSize.height() : height));
        }
        return pixmap;
    }
};