How to register QQuickAsyncImageProvider

[ocgltd]

I have created a QQuickAsyncImageProvider based image provider that I would like to use from my QML code, but at run time QML complains about "Invalid image provider"

I already have a QQMLExtensionPlugin based class containing:

void ImageProviderExtensionPlugin::registerTypes(const char *uri)
{
    Q_UNUSED(uri);
}


void ImageProviderExtensionPlugin::initializeEngine(QQmlEngine *engine, const char *uri)
{
    Q_UNUSED(uri);
    engine->addImageProvider("orchestrator", new OrchestratorImageProvider);
}

and I reference the image in QML as: source: "image://orchestrator/myimage.png"

What am I missing? Searching the Qt docs I see reference to creating a qmldir file (but I think that's just if I am creating an imageprovider as a lib). I also see another example that calls engine.addImageProvider but since I'm using a plugin class I don't think that's necessary.

Can someone fill in the blank for me?