Using QImage With QQuickImageProvider

问题

I have created a class that inherits QQuickImageProvider Class, but i want to use the requestImage() function of QQuickImageProvider to set the QImage variable , but i dont know how to do that as i need that QImage variable from a class object , which has been deifned in QML from ContextProperty and want to use the id variable as an index values to retrieve QImage from a List. Here is the main function code:

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    ImageProvider *imageProvider = new ImageProvider;
    QQmlApplicationEngine engine;
    PageBuffer p;
   engine.rootContext()->setContextProperty("p",&p);
   engine.load(QUrl(QStringLiteral("qrc:/main.qml")));
   engine.addImageProvider("images", imageProvider);

    return app.exec();
}

PageBuffer p contains a List of QImages that i need to present using QQuick ImageProvider when a certain index value for the List has been selected by the user. Here is the snippet of QML code where i want to pass the index value to the imageprovider, it shows an Image Element that will display one of the elements from the List of the Qimages that is saved in the PageBuffer object:

    Image{
                    x: 4
                    y: 4
                    height : imagerec.height
                    visible: true
                    width : imagerec.width
                    anchors.fill: imagerec
                    source:fileUrl
                    Text{
                        id:txt
                        x: 0
                        y: 71
                        text:"Sketch"+(index+1)
                        horizontalAlignment: txt.AlignHCenter
                        font.family: "Tahoma"
                        color:"#ffffff"

                    }

                    MouseArea {
                        anchors.rightMargin: -59
                        anchors.bottomMargin: -39
                        anchors.fill: parent
                        onClicked: {
                            p.index=index;
                            p.image=mod.get(index).fileUrl
                           images.image=p.img
                          //  main.source="image://image/1"

                    //                                main.source=p.image

                                  //        console.log(mod.get(index).fileUrl)
                            //              main.source=p.image;

                            //   currentimage=m.image;
                        }
                    }
                }

回答1:

You can set objectName of p in c++ code. Assume this name is MyObject. So now you can pass this name (as a string) to your image provider(imageprovider in this case):

main.source="image://imageprovider/MyObject"

As I understand you already have your own class, derived from QQuickImageProvider and overided requestImage. In your case id will be "MyObject". So now you easy can get real class by its objectName:

QQuickWindow *window = qobject_cast<QQuickWindow*>(engine.rootObjects()[0]);    
PageBuffer *p = window->findChild<PageBuffer *>(id);

I don't sure with accessing the root item, check it by yourself please.

UPDATED:

You can declare ImageProvider as:

imageprovider.h

class ImageProvider : public QQuickImageProvider
{
public:
    ImageProvider (QQmlEngine *engine,ImageType type, Flags flags = 0);
private:
    QQmlEngine *m_engine;
}

imageprovider.cpp

ImageProvider ::ImageProvider (QQmlEngine *engine, ImageType type, Flags flags)  :
    QQuickImageProvider(type,flags),
    m_engine(engine)
{
} 

QImage ImageProvider ::requestImage(const QString &id, QSize *size, const QSize &requestedSize)
{
    QQuickWindow *window = qobject_cast<QQuickWindow*>(m_engine.rootObjects()[0]);    
    PageBuffer *p = window->findChild<PageBuffer *>(id);
    // do with p what you want
}

main.cpp

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    QQmlApplicationEngine engine;
    ImageProvider *imageProvider = new ImageProvider(&engine,QQmlImageProviderBase::Image,0); 
    PageBuffer p;
    engine.rootContext()->setContextProperty("p",&p);
    engine.load(QUrl(QStringLiteral("qrc:/main.qml")));
    engine.addImageProvider("images", imageProvider);
    return app.exec();
}

来源：https://stackoverflow.com/questions/29929643/using-qimage-with-qquickimageprovider

标签

c++

qml

qimage

qlist