Itextsharp PDF 损坏

Question

I am working on this feature which takes a pdf from a database and signs the PDF with an image of the signature which needs to be retrieved from the database. I am using iTextSharp for this, but somehow it is not working and is corrupting my PDF in the database.

This is the code of my controller

public ActionResult Approve(int? id)
{
    ApplicationUser users = db.Users.Find(User.Identity.GetUserId());
    Reports reports = db.Reports.Find(id);

    if (reports == null || users == null) return View();

    byte[] content = reports.Content;
    byte[] signature = users.Signature; 

    iTextSharp.text.Image sigImg = iTextSharp.text.Image.GetInstance(signature);

    PdfReader reader = new PdfReader(content);
    using (MemoryStream ms = new MemoryStream())
    {
        PdfStamper stamper = new PdfStamper(reader, ms);

        sigImg.SetAbsolutePosition(0f,0f);

        sigImg.ScalePercent(90.0f); // 100.0f == same size


        //Give some space after the image
        sigImg.SpacingAfter = 1f;
        sigImg.Alignment = Element.ALIGN_BOTTOM;

        PdfContentByte over = stamper.GetOverContent(1);

        over.AddImage(sigImg);

        reports.Content = ms.ToArray();
        content = reports.Content;

        ms.Flush();
        db.SaveChanges();
        if(stamper!= null)
            stamper.Close();
        if(reader!= null)
            reader.Close();

        return File(content, "application/pdf");

        // Clean up

    }
}

What am I doing wrong here?

Answer 1

You retrieve the contents of the MemoryStream

reports.Content = ms.ToArray();

before you close the PdfStamper

if(stamper!= null)
    stamper.Close();

which means the MemoryStream does not yet contain the complete stamped PDF.

Thus, change the order of commands, in particular close the stamper before retrieving the bytes from ms .

As an aside: Why do you check stamper!= null ? It obviously cannot be null there...