qt在图片中绘制文本且不改变图片像素

QImage image;//= new QImage("qrc:\main\fundus_ui\resource\timg.jpg");
     bool ret=image.load("C:\\Users\\Administrator\\Desktop\\QTsucai\\test.jpg");

     QPainter painter(&image);

     painter.setRenderHint(QPainter::Antialiasing, true);

     painter.setPen(QPen(Qt::blue, 200, Qt::SolidLine, Qt::RoundCap, Qt::RoundJoin));
     painter.setFont(QFont(QString::fromLocal8Bit("宋体"),50,-1,false));//设置字体
     painter.drawText(160,160,211,204,Qt::AlignHCenter|Qt::AlignVCenter,QString::fromLocal8Bit("中国"));//绘制文本
     image.save("C:\\Users\\Administrator\\Desktop\\test.jpg");//绘制后的图片保存到本地
     QImage images;
      ret=images.load("C:\\Users\\Administrator\\Desktop\\test.jpg");
     qDebug()<<ret;
     QImage newImg = images.scaled(ui->label->width(), ui->label->height(),Qt::KeepAspectRatioByExpanding);
     ui->label->setPixmap(QPixmap::fromImage(newImg));//在lable中显示