效果如下：
我通过重写一个继承自QGraphicitem的类来实现上述功能，绘制重叠区域主要通过QPainterPath来实现，核心代码如下：
void myGraphicRectItem::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget) { QPen mPen= QPen(Qt::yellow); painter->setPen(mPen); //绘制旋转后的矩形 painter->drawPolygon(m_oldRectPolygon); //绘制旋转圆形 mPen.setWidth(2); mPen.setColor(Qt::green); painter->setPen(mPen); QPointF pf = getSmallRotateRectCenter(m_oldRectPolygon[0],m_oldRectPolygon[1]); QRectF rect = QRectF(pf.x()-10,pf.y()-10,20,20); painter->drawEllipse(rect);//绘制圆形 painter->drawPoint(pf);//绘制点 //有重叠的情况 if(!this->scene()->collidingItems(this).isEmpty()) { QPainterPath path,pathOthers; QList<QGraphicsItem *> lstcolliItems = this->scene()->collidingItems(this); int nColliNum = lstcolliItems.count(); for(int i = 0;i<nColliNum;i++) { QGraphicsItem* pTempItem = this->scene()->collidingItems(this)[i]; QPainterPath tempPath = pTempItem->shape(); tempPath.translate(pTempItem->pos());//转换到view中的坐标 pathOthers += tempPath;//记录与本item重叠的item的路径 } path.addPolygon(m_oldRectPolygon); path.translate(this->pos());//转换到view中的坐标 path &= pathOthers;//计算重叠部分的路径path path.translate(-this->pos().x(),-this->pos().y());//转换回本Item中的坐标 QBrush brush(Qt::cyan); mPen.setColor(Qt::blue); painter->setPen(mPen); painter->setBrush(brush); painter->drawPath(path);//绘制重叠区域 } }