qt svg图形写入pdf失败

qt svg图形写入pdf失败
//利用QFileDialog对话框选择文件存储路径
QString path = QFileDialog::getSaveFileName(this,tr("Open File"),".",tr("PDF Files(*.pdf)")); 

if(!path.isEmpty())
{
    //如果没有写后缀就自动加上
    if(QFileInfo(path).suffix().isEmpty())
        path.append(".pdf");
    //实例化该文件，并以只写的方式打开
    QFile pdfFile(path);
    if(!pdfFile.open(QIODevice::WriteOnly))
    {
        QMessageBox::warning(this,tr("write File"),tr("Cannot open file:\n%1").arg(path));
        return;
    }
    QPdfWriter *pdfWriter = new QPdfWriter(&pdfFile);               //实例化QPdfWriter
    QPainter *pic_painter = new QPainter(pdfWriter);                //实例化QPainter
    pdfWriter->setPageSize(QPagedPaintDevice::A4);                  //设置纸张为A4纸
    pdfWriter->setResolution(300);           //设置分辨率
    /******************************************************以下为自定义绘图**************************************/
    ////SVG渲染
    QSvgRenderer* svgRender = new QSvgRenderer(QString(QCoreApplication::applicationDirPath() + "/tools/handleFile/mark.svg"));
    QPixmap pixmap(100, 100);
    pixmap.fill(Qt::transparent);//设置背景透明
    QPainter p;
    p.begin(&pixmap);
    svgRender->render(&p);

    pic_painter->drawPixmap(50, 100, pixmap);

结果：pdf文件中没有svg图形内容