Convert jpeg image to thumbnail image in Qt

Question

A QImage needs to be finally shown as a thumbnail image in a QLabel. In between it's serialized in QByteArray and sent over the network. So, can we convert the QImage to QByteArray for thumbnail? Basically I want to avoid the QImage::scale() method as it's quite CPU consuming. Like QImage converted to a QByteArray which will hold data for thumbnail images.

Answer 1

On this case you cannot avoid QImage::scale. Why do you want? This is the answer to your question how to save QImage to QByteArray.

        QFile file(imagePath);
        if (file.open(QIODevice::ReadOnly)) {
            QByteArray bytes;
            QImage img;
            img = img.fromData(file.readAll());
            img = img.scaled(200, 100, Qt::IgnoreAspectRatio, Qt::FastTransformation);
            SetLabelImage(img);
            QBuffer buffer(&bytes);
            img.save(&buffer, "PNG");
        }