某些pdf文件水印不会显示使用iText

Question

Our company using iText to stamp some watermark text (not image) on some pdf forms. I noticed 95% forms shows watermark correctly, about 5% does not. I tested, copy 2 original pdf files, one was marked ok, other one does not ok, then tested in via a small program, same result: one got marked, the other does not. I then tried the latest version of iText jar file (version 5.0.6), same thing. I checked pdf file properties, security settings etc, seems nothing shows any hint. The result file does changed size and markd "changed by iText version...." after executed program.

Here is the sample watermark code (using itext jar version 2.1.7), note topText, mainText, bottonText parameters passed in, make 3 lines of watermarks show in the pdf as watermark.

Any help appreciated !!

public class WatermarkGenerator {

    private static int TEXT_TILT_ANGLE = 25;
    private static Color MEDIUM_GRAY = new Color(160, 160, 160);
    private static int SUPPORT_FONT_SIZE = 42;
    private static int PRIMARY_FONT_SIZE = 54;

    public static void addWaterMark(InputStream pdfInputStream,
        OutputStream outputStream, String topText, 
        String mainText, String bottomText) throws Exception {
        PdfReader reader = new PdfReader(pdfInputStream);
        int numPages = reader.getNumberOfPages();

        // Create a stamper that will copy the document to the output
        // stream.
        PdfStamper stamp = new PdfStamper(reader, outputStream);
        int page=1;

        BaseFont baseFont = 
            BaseFont.createFont(BaseFont.HELVETICA_BOLDOBLIQUE,
                BaseFont.WINANSI, BaseFont.EMBEDDED);

        float width;
        float height;

        while (page <= numPages) {
            PdfContentByte cb = stamp.getOverContent(page);
            height = reader.getPageSizeWithRotation(page).getHeight() / 2;
            width = reader.getPageSizeWithRotation(page).getWidth() / 2;

            cb = stamp.getUnderContent(page);
            cb.saveState();
            cb.setColorFill(MEDIUM_GRAY);

            // Top Text
            cb.beginText();
            cb.setFontAndSize(baseFont, SUPPORT_FONT_SIZE);
            cb.showTextAligned(Element.ALIGN_CENTER, topText, width,
                    height+PRIMARY_FONT_SIZE+16, TEXT_TILT_ANGLE);
            cb.endText();

            // Primary Text
            cb.beginText();
            cb.setFontAndSize(baseFont, PRIMARY_FONT_SIZE);
            cb.showTextAligned(Element.ALIGN_CENTER, mainText, width,
                    height, TEXT_TILT_ANGLE);
            cb.endText();

            // Bottom Text
            cb.beginText();
            cb.setFontAndSize(baseFont, SUPPORT_FONT_SIZE);
            cb.showTextAligned(Element.ALIGN_CENTER, bottomText, width,
                    height-PRIMARY_FONT_SIZE-6, TEXT_TILT_ANGLE);
            cb.endText();
            cb.restoreState();

            page++;
        }

        stamp.close();
    }
}

Answer 1

We solved problem by change Adobe LifecycleSave file option. File->Save->properties->Save as, then look at Save as type, default is Acrobat 7.0.5 Dynamic PDF Form File, we changed to use 7.0.5 Static PDF Form File (actually any static one will work). File saved in static one do not have this watermark disappear problem. Thanks Mark for pointing to the right direction.

Answer 2

You're using the underContent rather than the overContent. Don't do that. It leaves you at the mercy of big, white-filled rectangles that some folks insist on drawing first thing. It's a hold over from less-than-good PostScript interpreters and hasn't been necessary for Many Years.

---

Okay, having viewed your PDF, I can see the problem is that this is an XFA-based form (from LiveCycle Designer). Acrobat can (and often does) rebuild the entire file based on the XFA (a type of xml) it contains. That's how your changes are lost. When Acrobat rebuilds the PDF from the XFA, all the existing PDF information is pitched, including your watermark.

The only way to get this to work would be to define the watermark as part of the XFA file contained in the PDF.

Detecting these forms isn't all that hard:

PdfReader reader = new PdfReader(...);
AcroFields acFields = reader.getAcroFields();
XfaForm xfaForm = acFields.getXfaForm();
if (xfaForm != null && xfaForm.isXfaPresent()) {
  // Ohs nose.
  throw new ItsATrapException("We can't repel XML of that magnitude!");
}

Modifying them on the other hand could be Quite Challenging, but here's the specs .

Once you've figured out what needs to be changed, it's a simple matter of XML manipulation... but that "figure it out" part could be interesting .

Good hunting.