iText7 Convert PDF to image while maintaining the highlighting

Question

I am using iText7(C#) and am looking for a way to convert a pdf page to image leave the highlighting. The goal is to create a rendered image (not searchable) of the pdf.

I have tried with this code but without success

using (PdfWriter pdfWriter = new PdfWriter(destinationFilename, new WriterProperties().SetPdfVersion(PdfVersion.PDF_2_0)).SetSmartMode(true))
using (PdfReader pdfReader = new PdfReader(sourceFilename))
using (PdfDocument pdfSource = new PdfDocument(pdfReader))
using (PdfDocument pdfDestination = new PdfDocument(pdfWriter))
using (Document document = new Document(pdfDestination))
{
    int pages = pdfSource.GetNumberOfPages();
    for (int i = 1; i <= pages; i++)
    {
        PdfPage page = pdfSource.GetPage(i);

        PdfFormXObject pdfFormXObject = page.CopyAsFormXObject(pdfDestination);
        iText.Layout.Element.Image image = new iText.Layout.Element.Image(pdfFormXObject);
        document.Add(image);
    }
}

Do you have any idea how to do this?