QT 预览打印 添加水印

使用QT的QPrintPreviewDialog很容易实现对textedit中文本的打印预览功能,代码如下:

void proofreadtext::on_pushButton_3_clicked()
{
    QPrinter printer(QPrinter::ScreenResolution);
    
    printer.setPageSize(QPrinter::A4);
    QPrintPreviewDialog preview(&printer);
    connect(&preview, SIGNAL(paintRequested(QPrinter*)), this, SLOT(getPreviewData(QPrinter*)));
    preview.exec();
}
void proofreadtext::getPreviewData(QPrinter *printer)
{
    ui->textEdit_entertext->print(printer);
}

但如何实现在预览的同时添加水印?

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