Capturing Image via CaptureToBuffer not works on Android

  • Hi,
    I just tried to capture an image from the camera directly from the buffer. No matter what I try nothing works unfortunatley.

    1.) Via QCameraImageCapture:

    void Qml::iniObjects()
    m_pRootObj = m_pEngine->rootObjects().first();
    QObject *qmlCamera = m_pRootObj->findChild<QObject*>("oCamera");
    m_pCamera = qvariant_cast<QCamera *>(qmlCamera->property("mediaObject"));
    m_pImgCapt = new QCameraImageCapture(m_pCamera);
    connect(m_pImgCapt,SIGNAL(imageAvailable(int,const QVideoFrame&)), this, SLOT(updImageAvailable(int,const QVideoFrame&)));
    bool dest = m_pImgCapt->isCaptureDestinationSupported(QCameraImageCapture::CaptureToBuffer);
    qDebug() << dest; **-> true**
    QList<QVideoFrame::PixelFormat> format = m_pImgCapt->supportedBufferFormats();
    qDebug() << format; **-> (Format_Jpeg)**
    void Qml::updImageAvailable(int id, const QVideoFrame &buffer) {
        qDebug() << "Image";

    Result: No error, no signal

    2.) Via QMediaService: Same code as before, excepted the following.

    QMediaService *service = m_pCamera->service();
    QMediaControl *control = service->requestControl(QCameraImageCaptureControl_iid);
    QCameraImageCaptureControl *captureControl = qobject_cast<QCameraImageCaptureControl*>(control);
    connect(captureControl,SIGNAL(imageAvailable(int,const QVideoFrame&)), this, SLOT(updImageAvailable(int,const QVideoFra@me&)));

    Result: No error, no signal

    Anyone an idea?

    Thanks in advance...

  • connect(captureControl,SIGNAL(imageAvailable(int,const QVideoFrame&)), this, SLOT(updImageAvailable(int,const QVideoFra@me&))); has a @ in it...

    could you use the new connect syntax:connect(m_pImgCapt,&QCameraImageCapture::imageAvailable, this, &Qml::updImageAvailable); and connect(captureControl,&QCameraImageCaptureControl::imageAvailable, this, &Qml::updImageAvailable);

    did you name your class Qml? I see a huge potential for naming clashes...

  • Moderators

    @PowerNow Check if the signal and slot connection was successful. connect returns the status.

  • @p3c0 and @VRonin : Thxs for your fast response!
    I checked all your proposals but no difference. Regarding @ this was a inexplicable copy paste failure. But fortunately I found the reason. Maybe others are interessted:

    As I read the official docu for "QCameraImageCapture::capture" I found no hint regarding the signal "QCameraImageCapture::imageAvailable()". So I thought falsely that this signal is automatically created everytime a QVideoFrame is ready. But obviously also this signal is created only after calling "QCameraImageCapture::capture()". As my understanding this case is not considered in the docu.
    This also means if you set QCameraImageCapture::setCaptureDestination(QCameraImageCapture::CaptureToBuffer) there is no picture saved properly, independed if the passed QString to "::capture(""filename") is empty or not.

  • @PowerNow Hello r u using QML? I capture images using QCamera. Check this thread from yesterday :)

Log in to reply