无法打印数字签名

Question

我使用ModelDoc创建了一个pdf文档。创建后，我使用PDFSharp在文档中插入数字签名。

正确看到数字签名，我也能够执行签名验证的正常任务。

但是，打印文档时不会打印数字签名。我已经尝试过使用“文档和标记”和“文档和邮票”。

但是，签名仍未打印。这是数字签名的代码。

void ISignatureAppearanceHandler.DrawAppearance(XGraphics gfx, XRect rect)
    {
        string signtext = "This is a digital signature";

        XFont font = new XFont("Verdana", 8.0, XFontStyle.Regular);
        XPoint xPoint = new XPoint(0.0, 0.0);

        gfx.DrawRectangle(
            XBrushes.LightBlue, xPoint.X, 
            xPoint.Y, rect.Width, rect.Height
        );

        XTextFormatter xTextFormatter = new XTextFormatter(gfx);

        xTextFormatter.DrawString(
            signtext, font, 
            new XSolidBrush(
                XColor.FromKnownColor(XKnownColor.Black)
            ), 
            new XRect(
                xPoint.X, xPoint.Y, rect.Width, rect.Height
            ),  
           XStringFormats.TopLeft
        );
    }

Answer 1

尝试在启动PdfSignatureHandler之前打印文本它对我来说很好。

 private static void SignExisting()
    {
        double height = 40;
        double width = 200;
        double x = 0;
        double y = 0;    
        PdfDocument pdfDocument = PdfReader.Open(path);
        PdfPage pp = pdfDocument.Pages[0];
        var cert = GetCertificate();
        string signtext = "Digitaly Signed by " + cert.GetNameInfo(X509NameType.SimpleName, false);           
       XGraphics gfx = XGraphics.FromPdfPage(pp);       
            XFont font = new XFont("Arial", 10, XFontStyle.Regular);
            gfx.DrawString(signtext, font, XBrushes.Black, new XRect(x, pp.Height - y, pp.Width, pp.Height), XStringFormats.TopLeft);
            gfx.DrawString("Date: " + DateTime.Now.ToString(), font, XBrushes.Black, new XRect(x, pp.Height - y, pp.Width, pp.Height), XStringFormats.TopLeft);  
        PdfSignatureOptions options = new PdfSignatureOptions
        {
            ContactInfo = cert.GetNameInfo(X509NameType.SimpleName, false),
            Location = cert.Subject,
            Reason = "",
            Rectangle = new XRect(x, y, width, height),
            AppearanceHandler = new SignAppearenceHandler()
        };
        PdfSignatureHandler pdfSignatureHandler = new PdfSignatureHandler(cert, null, options);
        pdfSignatureHandler.AttachToDocument(pdfDocument);
        Stream stream = new MemoryStream();
        pdfDocument.Save(stream);
    }