QCamera + QCameraViewfinder: how to mirror the the image displayed in the viewfinder?

[SGaist]

What OS are you running ? It might be that the backend doesn't provide that control.

[Violet Giraffe]

Windows 10.

[nicesw123]

how to mirror the the image displayed in the viewfinder?

+1

Actually
+1000

This is a very good question!
I also want to mirror the image (flip it left to right)!

PS:
I'm using Debian Testing, which requires these packages, to get QCamera working: qt5-default, libqt5multimedia5, libqt5multimedia5-plugins, libqt5multimediaquick-p5, libqt5multimediawidgets5, qml-module-qtmultimedia, qtmultimedia5-dbg, qtmultimedia5-dev

[SGaist]

Just a quick update:

    QVideoRendererControl *rendererControl = camera.service()->requestControl<QVideoRendererControl *>();
    if (rendererControl) {
        QAbstractVideoSurface *surface = rendererControl->surface();
        QVideoSurfaceFormat format = surface->surfaceFormat();
        format.setProperty("mirrored", true);

        surface->stop();
        surface->start(format);
    } else {
        qDebug() << "Backend doesn't provide a video renderer control";
    }

[Violet Giraffe]

Thanks, but still no. rendererControl is null, and I tried executing your snippet both before and after camera.start() call.

[SGaist]

Can you check what plugin is loaded ? It should be either the WMF or DirectX plugin. IIRC the DX plugin has the control.

[Violet Giraffe]

I can't see either. Here's the complete list of all the .dlls loaded.
I can, however, see an odd warning. I don't have a slightest idea if it's related, but probably not:

D3D11CreateDevice: Flags (0x2) were specified which require the D3D11 SDK Layers for Windows 10, but they are not present on the system.
These flags must be removed, or the Windows 10 SDK must be installed.
Flags include: D3D11_CREATE_DEVICE_DEBUG

[SGaist]

Sorry, I meant start your application with QT_DEBUG_PLUGINS set to 1.

[Violet Giraffe]

Is it an environment variable or a project define?

[SGaist]

Environment variable that you can set in the Run part of the Project panel.

[Violet Giraffe]

Here's the list. Can't see anything named WMF, but I guess I need to know the exact name to look for.

[nicesw123]

@Violet-Giraffe said:

Thanks, but still no. rendererControl is null

Same for Debian (and it's variants [Ubuntu, etc.])

[nicesw123]

Maby the way to do this for now...
(i.e. until the qt developers realize the value of extending QCameraImageProcessing or QCameraViewfinder to allow mirroring (flipping) the image)

...is to "derive from QAbstractVideoSurface" as shown here: http://doc.qt.io/qt-5/cameraoverview.html#viewfinder (find some example code there, showing rotation)

[SGaist]

DSEngine -> DirectShow. The plugin it self has the control but it seems it's not accessible yet.

If you are wiling to re-build the plugin, that can be modified.

[Violet Giraffe]

@SGaist, it depends on how difficult it is to build Qt 5 nowadays (I remember it being a pain because of WebKit that I didn't even need, hopefully that's fixed now). Let me check nicesw123's suggestion first.

[Devopia53]

Qt/C++ already provides that functionality. You can easily implement flipping feature if you use the following classes.

QGraphicsView, QGraphicsScene, QCamera, QVideoWidget, QTramsform

[Violet Giraffe]

@Devopia53, how can I connect those to QCamera if the only thing camera accepts is QCameraViewfinder?
P. S. Nvm, it accepts QVideoWidget. Still not quite sure how to connect the parts you've listed. A little help, please? :)

[Devopia53]

@Violet-Giraffe
QCameraViewfinder is not a solution for flipping. Instead, use the QAbstractVideoSurface. But it is poor display performance.

Samples on how to use the QGraphicsView are as follows: I wish you a note.

auto camera = new QCamera;
auto widget = new QVideoWidget;
QTransform matrix(-1,0,0,0,1,0,0,0,1); // m11=-1 : flipping horizontal

graphicsView->setScene(new QGraphicsScene);
graphicsView->show();

auto proxyWidget = graphicsView->scene()->addWidget(widget);

proxyWidget->setTransform(matrix);
camera->setViewfinder(widget);
camera->start();

[Violet Giraffe]

@Devopia53, thanks, but I think you're missing something. proxyWidget is not used here. AndQTransform has no effect on the widget, although I do see the image just as I did with QCameraViewfinder.

[Violet Giraffe]

Any further ideas? I'm stuck here.