Qml Canvas draw QImage

My task is to transfer what is drawn in a user canvas to a QImage. In this case, the QML canvas must be created dynamically, since there can be many QImages.

I need to implement this code:

QList<QImage> imgs;

for (int i = 0; i < elements.length(); ++i) {
    QImage img = paintImageElements(elements[i]);
    imgs.append(img);
}

Trying to implement this:

QImage paintImageElements(const QString& elements) {
    QQmlContext* context = QQmlEngine::contextForObject(this);
    QQmlEngine *engine = context->engine();
    QQmlApplicationEngine *appEngine = qobject_cast<QQmlApplicationEngine*>(engine);
    QQmlComponent imageSceneComp(engine, QUrl(QStringLiteral("qrc:/ImagePainter/ImageScene.qml")));
    QVariantMap initialProps;
    initialProps["elements"] = elements;
    QObject *imageSceneObj = imageSceneComp.createWithInitialProperties(initialProps, appEngine->rootContext());
    auto grabResult = item->grabToImage();
    return grabResult->image();
}

How do I implement the paintImageElements function correctly?

Because at the moment I get an error:

qrc:/ImagePainter/ImageScene.qml:7:1: QML ImageScene: grabToImage: item is not attached to a window