如何从路径加载 QImage？

Question

I captured an Image with camera in my qt quick application.I want to send the path to my c++ code and load that Image in c++ QImage .But the Path is image://camera/preview_1 and I don't know How work with that path?

Camera {
    id: camera

    imageCapture {
        onImageCaptured: {
            console.log("Preview = "+preview);
            photoPreview.source = preview
            console.log("CapturedImagePath => "+camera.imageCapture.capturedImagePath);
            up.loadImage(preview);
        }
}

c++ class

void UserProfile::loadImage(QString path)
{    
    QUrl imageUrl(path);
    qWarning()<<"imageUrl.host()=>"<<imageUrl.host();
    qWarning()<<"imageUrl.path()=>"<<imageUrl.path();
    qWarning()<<"imageUrl.toLocalFile()=>"<<imageUrl.toLocalFile();
    bool isOpend= m_image.load(path); //m_image is an QImage object
    qWarning()<<"Image loaded=> "<<isOpend;
}

Application output

D MyApp: qml: Preview = image://camera/preview_1
D MyApp: qml: CapturedImagePath =>
W MyApp: imageUrl.host()=> "camera"
W MyApp: imageUrl.path()=> "/preview_1"
W MyApp: imageUrl.toLocalFile()=> ""
W MyApp: Image loaded=> false

Answer 1

The URL image://camera/preview_1 means that the image data is living in a QQuickImageProvider instance. Probably, it's a QQuickImageProvider instance created by Camera .

As the UserProfile instance is living in the same QQmlEngine as the camera lives, you can

void UserProfile::loadImage(const QString &path)
{
    auto myQmlEngine = qmlEngine(this);
    if(myQmlEngine==nullptr)
        return;

    QUrl imageUrl(path);
    auto provider = reinterpret_cast<QQuickImageProvider*>( myQmlEngine->imageProvider(imageUrl.host()));

    if (provider->imageType()==QQuickImageProvider::Image){
        QImage img = provider->requestImage(imageUrl.path().remove(0,1),nullptr,QSize());
        // do whatever you want with the image
    } 
}

Be careful with the reinterpret_cast . You also have to make sure that the QQuickImageProvider::imageType() is returning QQmlImageProviderBase::Image .

and you could also use capturedImagePath instead of the preview URL to prevent this complexity if it could be an option for your usecase.