RadialGradentBrush

        QRadialGradient rg;
        rg.setColorAt(0,Qt::white);
        rg.setColorAt(1,Qt::black);
        rg.setRadius(300);
        rg.centerRadius();
        rg.setCenter((QPointF(165,140)));
        QBrush brush1(rg);  //QColor(0, 0, 255, 255));