Qpainter 画图 画矩形

 QPainter painter(this);
    painter.setBrush(Qt::black);
    painter.drawRect(0, 0, this->width(), this->height());//先画成黑色
    if(m_Image.size().width() <= 0)
        return;
    //将图像按比例缩放成和窗口一样大小
    QImage img = m_Image.scaled(this->size(), Qt::KeepAspectRatio);
    int x = this->width() - img.width();
    int y = this->height() - img.height();
    x /=  2;
    y /= 2;
    painter.drawImage(QPoint(x, y), img); //画出图像

    //定义画笔
    QPen pen;
    pen.setWidth(5);
    pen.setColor(QColor(0,160,230));
    pen.setStyle(Qt::SolidLine);

    painter.setPen(pen);
   // p.drawLine(50,50,150,50);
   //p.drawLine(50,50,50,150);

    //创建画刷 填充区
    QBrush brush;
    //brush.setColor(Qt::white);
    //brush.setStyle(Qt::Dense6Pattern);

    painter.setBrush(brush);

    // 画矩形；
    painter.drawRect(50,100,100,200);

    painter.end();