//first create a pixmap object
QPixmap pixmapObject(":Images/myimage.png");
//now create a QGraphicsPixmapItem
QGraphicsPixmapItem * myImagePixmapItem
= new QGraphicsPixmapItem();
//add the resized QGraphicsPixmapItem to the pixmap
myImagePixmapItem->setPixmap(
pixmapObject.scaledToHeight(50,
Qt::SmoothTransformation));
The scaledToHeight function in the last line could be either scaled, scaledToWidth or scaledToHeight. scaled allows you to set both the width and height of the object where as the other 2 will scale the other side automatically so that the aspect ratio of the pixmap is preserved.