Qt之路径叠加透明

注：Qt中路径叠加效果控制由Qt::FillRule::WindingFill与Qt::FillRule::OddEvenFill控制实现。

void Widget::paintEvent(QPaintEvent *event)
{
    Q_UNUSED(event);

    QPainter painter(this);
    painter.fillRect(this->rect(),QBrush(QColor(255,255,255)));
    painter.setRenderHint(QPainter::Antialiasing);//抗锯齿

    painter.fillRect(this->rect(),QBrush(QColor(0,0,0)));

    painter.save();
    painter.setPen(QColor(0,255,0));
    painter.translate(this->width()/2,this->height()/2);

    QVector<QPointF> vecPF;
    for (auto i=0;i<5;i++) {
        QPointF ptEnd(100.0*cos(72.0*i*M_PI/180.0),100.0*sin(72.0*i*M_PI/180.0));
        vecPF.push_back(ptEnd);
    }

    QPolygonF plgF;
    QPainterPath path,path1;
    plgF<<vecPF[4]<<vecPF[1]<<vecPF[3]<<vecPF[0]<<vecPF[2];
    path.addPolygon(plgF);
    path.setFillRule(Qt::FillRule::WindingFill);
//    path.setFillRule(Qt::FillRule::OddEvenFill);
    painter.fillPath(path,QBrush(QColor(255,0,0)));
    painter.restore();

    QPolygonF plyg1,plyg2;
    plyg1<<QPointF(10,10)<<QPointF(110,10)<<QPointF(110,110)<<QPointF(10,110);
    plyg2<<QPointF(20,20)<<QPointF(100,20)<<QPointF(100,100)<<QPointF(20,100);
    path1.setFillRule(Qt::FillRule::WindingFill);
//    path1.setFillRule(Qt::FillRule::OddEvenFill);
    path1.addPolygon(plyg1);
    path1.addPolygon(plyg2);
    painter.fillPath(path1,QBrush(QColor(255,0,0,100)));
}