可以用QPixmap的静态方法
QPixmap grabWidget ( QWidget * widget, const QRect & rectangle )
QPixmap grabWidget ( QWidget * widget, int x = 0, int y = 0, int width = -1, int height = -1 )
QPixmap grabWindow ( WId window, int x = 0, int y = 0, int width = -1, int height = -1 )
