Convert QImage to QObject

MyNameIsQt

I want to draw the qimage on the canvas through the qwebchannel.
In order to pass qimage to js, I need to convert QImage to QObject.
But the following function throws an error and I don't know why.
How to safely convert QImage to QObject?

public slots:
    QObject * getImgObject();
....

QObject *WPubManager::getImgObject()
{
// convert QImage to QObject and return value
    if(m_pBkgnd){
        QByteArray byteArray;
        QBuffer buffer(&byteArray);
        buffer.open(QIODevice::WriteOnly);
        
        // func getBkgndImg return QImage
        m_pBkgnd->getBkgndImg().save(&buffer, "WEBP");

        QJsonObject imageObject;
        imageObject["data"] = QString::fromLatin1(byteArray.toBase64().data());

        imgObject->setProperty("image", QVariant::fromValue(imageObject));
    }else{
        qDebug() << "no Bkgnd";
    }
    return imgObject;
}

// canvas.html

 var wpubManager;
    if (typeof QWebChannel !== 'undefined') {
        new QWebChannel(qt.webChannelTransport, function (channel) {
            wpubManager = channel.objects.wpubManager;
            console.error('wpubManager:', wpubManager);
        });
    } else {
        console.error("QWebChannel is not defined. Make sure qwebchannel.js is properly loaded.");
    }

    var imageData;
    function drawCanvas(){
        **var imageObject = wpubManager.getImgObject();**
        var base64Image = imageObject.image.data;

        var canvas = document.getElementById("myCanvas");
        var context = canvas.getContext("2d");

        var img = new Image();
        img.src = "data:image/webp;base64," + base64Image;
        img.onload = function() {
            context.drawImage(img, 0, 0);
        };
    }

ChrisW67

@MyNameIsQt said in Convert QImage to QObject:

But the following function throws an error and I don't know why.

It may have been helpful to post the actual error message.

How to safely convert QImage to QObject?

You don't. It should be something like this:

From C++, register a WPubManager object with your QWebChannel object.
From JS, access a property of that WPubManager object containing your Base64 encoded image.

MyNameIsQt

@ChrisW67
thank you
I couldn't put the following code together. This is my fault.

void WpubEditor::on_Open_wpub_triggered()
{
    QString fileName = QFileDialog::getOpenFileName(this, tr("Open wpub file"), "", tr("wpub Files (*.wPub)"));
    if (!fileName.isEmpty()) {      

        if (!m_pPubManager)
        {
            QString htmlPath = QFileInfo(__FILE__).dir().absolutePath() + "/canvas.html";

            QFile file(htmlPath);
            if (file.exists()) {
                webView->load(QUrl::fromLocalFile(htmlPath));
            } else {
                qDebug() << "Failed to load canvas.html. File not found.";
            }

            m_pPubManager = new WPubManager(this, nullptr);
            channel->registerObject("wpubManager", m_pPubManager);
        }

        if (m_pPubManager->OpenWPub(fileName)){
            updateStatusBar(fileName);
            setMenuActionStatus(true);
        } else {
            qWarning("Couldn't open file.");
        }

    }
}