How to set opacity in QT brush

Question

How can i set the background color with an opacity when using QT Creator and C++.

In this case I want the QT::yellow and QT::Green to both have an opacity of 70%.

    if (isSelected()) {
        painter->setPen(QPen(Qt::darkYellow));
        painter->setBrush(Qt::yellow);
    } else {
        painter->setPen(QPen(Qt::darkGreen));
        painter->setBrush(Qt::green);
    }

Answer 1

You need to set the alpha channel on the color.

QColor green70 = Qt::green;
green70.setAlphaF( 0.7 );
painter->setBrush( green70 );