I have both text and image in QLabel, so setPixmap won't satisfy my requirement.
As far as I know, QLabel can load image from file by setting HTML label <img src="path_to_file" />. But how can I load image from memory(e.g. QImage)?  Because some images are frequently used, it may have performance problem loading the same image from file every time.
You can also set stylesheet for your QLabel as:-
            QLabel{
                background-image: url(/images/button.png);
How to insert QImage(or sth like that) into QLabel?