Qt 渐变色Gradient

线性渐变 QLinearGradient
弧度渐变 QConicalGradient
辐射渐变 QRadialGradient

    QPainter painter(this);    //线性渐变    QLinearGradient linearGradient(0,0,150,150);    linearGradient.setColorAt(0.2,Qt::white);    linearGradient.setColorAt(0.6,Qt::blue);    linearGradient.setColorAt(1.0,Qt::yellow);    painter.setBrush(QBrush(linearGradient));    painter.drawEllipse(0,0,200,150);    //保存当前的painter 放到堆中 save()函数必须有对应的restore()函数    //restore()函数 恢复painter的状态(从堆中取出来)    painter.save();

    painter.translate(200,0);   //以原坐标的(200,0)为新的坐标系坐标原点(0,0)    const int r = 100;    painter.setRenderHint(QPainter::Antialiasing,true);    //弧度渐变    //弧度渐变由圆心(xc,yc)和一个角度a定义。颜色从圆心开始像表的秒针一样扩散。    //QConicalGradient(qreal cx, qreal cy, qreal angle)  圆心在坐标原点(0,0)角度从60度开始    QConicalGradient conicalGradient(0,0,60);    conicalGradient.setColorAt(0.0,Qt::red);//    conicalGradient.setColorAt(60.0/360.0,Qt::yellow);//    conicalGradient.setColorAt(120.0/360.0,Qt::green);//    conicalGradient.setColorAt(180.0/360.0,Qt::cyan);//    conicalGradient.setColorAt(240.0/360.0,Qt::blue);//    conicalGradient.setColorAt(300.0/360.0,Qt::magenta);    conicalGradient.setColorAt(1.0,Qt::yellow);    //translate(r,r)  以原坐标的(r,r)为新的坐标系坐标原点(0,0)cx,cy  即相对于窗口(300,100)    painter.translate(r,r);    //QBrush brush(brush Style);    QBrush brush(conicalGradient);    painter.setPen(Qt::NoPen);    painter.setBrush(brush);    painter.drawEllipse(QPoint(0,0),r,r);    painter.save();

//辐射渐变    //圆心(0,0)cx,cy 角度0 radius 焦点(30,30)fx,fy开始向外扩散    painter.translate(0,200);    QRadialGradient radialGradient(0,0,100,50,50);    radialGradient.setColorAt(0,Qt::green);    radialGradient.setColorAt(0.8,Qt::red);    painter.translate(r,r);    painter.setBrush(QBrush(radialGradient));    painter.drawEllipse(QPoint(0,0),r,r);    painter.save();    //辐射渐变    //QRadialGradient radialGradient(310,110,100,330,130);    ////创建了一个QRadialGradient对象实例，参数分别为中心坐标，半径长度和焦点坐标,如果需要对称那么中心坐标和焦点坐标要一致    //radialGradient.setColorAt(0,Qt::green);    ////radialGradient.setColorAt(0.2,Qt::white);    //radialGradient.setColorAt(0.4,Qt::blue);    ////radialGradient.setColorAt(0.6,Qt::red);    //radialGradient.setColorAt(1.0,Qt::yellow);    //painter.setBrush(QBrush(radialGradient));    //painter.drawEllipse(210,10,200,200);//在相应的坐标画出来    painter.restore();