Distinguish between text message and image message sent from server (both encoded in qstring)

[SGaist]

This is wrong on several levels:

• Why load your image in a QImage ? You want to transmit the content of the file, no ?
• JSON is text based, you are trying to send binary data

If you want to send binary data in JSON you have to first convert them using e.g. base64.

Since you are sending JSON anyway, why not have a field that states the type of the content of params rather than doing guesses ?

[Vasudha]

Having a type field is a good idea.
And yeah, I just want to transmit the content of the file. Shouldn't I be loading the image first? How else can it be done?

[jsulm]

@Vasudha You need to encode the content of the image file (no need to use QImage, just read the file using QFile) as base64 and add this encoded string as a field in your JSON:

{"type": "image", "data": ".PUT HERE BASE64 ENCODED IMAGE DATA"}

[Vasudha]

Okay So I'm sending msgs like this-

    QFile file(fileName);
    if (!file.open(QFile::ReadOnly)) {
        qDebug() << "Cannot open the selected file";
        return;
    }
    QByteArray block;
    block = file.readAll();
    block.toBase64();

    QString message(block);
    QString roomID("rID");
    QString type("image");
    qDebug() << "base64 image- " << message;

    QString json = "{\"rid\": \"%1\", \"msg\": \"%2\", \"type\": \"%3\"}";
    json = json.arg(roomID, message, type);

    sendMessage("sendMessage", QJsonDocument::fromJson(json.toUtf8()));

And receiving them like-

            QString type = result.value("type").toString();
            QString msg = result.value("msg").toString();
            
            if (type == "image"){
                QByteArray decodedImage;
                QByteArray image;
                QPixmap pixmap;
                QLabel label;

                decodedImage.append(msg);
                image = QByteArray::fromBase64(decodedImage);
                pixmap.loadFromData(image,0,Qt::AutoColor);
                label.setPixmap(pixmap);
                label.show();
             }

But only "����" this is displayed instead of the image.

[SGaist]

Use QByteArray directly rather than QString, that will avoid unless conversions.

Also your label variable only exists for the lifetime of the if block in case of type being image so it won't even be shown.

[Vasudha]

@SGaist After correcting this part too the result was same. I realize I have been mixing QML with QWidgets and that's what is causing problems. Is there any other way of receiving images without using QWidgets?

[SGaist]

Do you mean showing images ?

[VRonin]

@Vasudha said in Distinguish between text message and image message sent from server (both encoded in qstring):

block.toBase64();

That is a const method. Do you mean block=block.toBase64();?

[Vasudha]

@SGaist yes

[Vasudha]

@VRonin yeah

[VRonin]

QFile file(fileName);
    if (!file.open(QFile::ReadOnly)) {
        qDebug() << "Cannot open the selected file";
        return;
    }
    const QString block = QString::fromLatin1(file.readAll().toBase64());
const QString roomID("rID");
    const QString type("image")
QJsonObject jSonImage;
jSonImage.insert("rid",roomID);
jSonImage.insert("type",type);
jSonImage.insert("msg",block);
sendMessage("sendMessage", QJsonDocument(jSonImage));

[Vasudha]

@VRonin This was very smart. The image is being sent successfully but how to show it (at receiving end) without using QWidgets (after decoding it)?

[SGaist]

A QtQuick Image element ?

[Vasudha]

Thank you everyone :)