1. 帮助文档中,提到了如果更改transform origin point,要设置setTransformOriginPoint函数的;
void QGraphicsItem::setScale ( qreal factor )
Sets the scale factor of the item. The default scale factor is 1.0 (i.e., the item is not scaled). A scale factor of 0.0 will collapse the item to a single point. If you provide a negative scale factor, the item will be flipped and mirrored (i.e., rotated 180 degrees).
The item is scaled around its transform origin point, which by default is (0, 0). You can select a different transformation origin by calling setTransformOriginPoint().