Pfthb

I am using this code: https://www.tutorialspoint.com/pdfbox/pdfbox_inserting_image.htm

To help me add an image to an existing PDF. The problem is that the file it creates is a blank page with only the image on it.

Here is my code:

public void signPDF(PdfDTO pdfDTO) throws IOException
 //Loading an existing document
 File file = new File(getAbsolutePdfPath(pdfDTO));
 PDDocument doc = PDDocument.load(file);

 //Retrieving the page
 PDPage page = doc.getPage(0);

 //a test to ensure the doc is loading correctly
 PDDocument testDoc = new PDDocument();
 testDoc.addPage(page);
 testDoc.save("C:" + File.separator + "Users" + File.separator + "kdotson" + File.separator + "Documents" + File.separator + "test.pdf");
 testDoc.close(); //this file is good so I know the doc is loading correctly

 //Creating PDImageXObject object
 PDImageXObject pdImage = PDImageXObject.createFromFile("C://test_images/signature.pdf", doc);

 //creating the PDPageContentStream object
 PDPageContentStream contents = new PDPageContentStream(doc, page);

 //Drawing the image in the PDF document
 contents.drawImage(pdImage, 0, 0);

 //Closing the PDPageContentStream object
 contents.close();

 //Saving the document
 doc.save(new File(getSignedPdfLocation(pdfDTO))); //the created file has the image on it, so I know the image is loading correctly

 //Closing the document
 doc.close();
 

As far as I can tell, what I'm doing should work, and I don't get any errors, so what gives?

Please also have a look at the JavaDocs and sources of the library you try to work with. You create a PDPageContentStream:

PDPageContentStream contents = new PDPageContentStream(doc, page);

This conductor is documented to overwrite all existing content streams of this page:

/**
 * Create a new PDPage content stream. This constructor overwrites all existing content streams
 * of this page.
 *
 * @param document The document the page is part of.
 * @param sourcePage The page to write the contents to.
 * @throws IOException If there is an error writing to the page contents.
 */
public PDPageContentStream(PDDocument document, PDPage sourcePage) throws IOException

Thus, you have to use a different constructor which keeps the current page contents, e.g.

/**
 * Create a new PDPage content stream.
 *
 * @param document The document the page is part of.
 * @param sourcePage The page to write the contents to.
 * @param appendContent Indicates whether content will be overwritten, appended or prepended.
 * @param compress Tell if the content stream should compress the page contents.
 * @param resetContext Tell if the graphic context should be reset. This is only relevant when
 * the appendContent parameter is set to @link AppendMode#APPEND. You should use this when
 * appending to an existing stream, because the existing stream may have changed graphic
 * properties (e.g. scaling, rotation).
 * @throws IOException If there is an error writing to the page contents.
 */
public PDPageContentStream(PDDocument document, PDPage sourcePage, AppendMode appendContent,
 boolean compress, boolean resetContext) throws IOException

Thus

PDPageContentStream contents = new PDPageContentStream(doc, page, AppendMode.APPEND, true, true);

should make your code work as desired.

Alternatively, if you want the image in the background, try

PDPageContentStream contents = new PDPageContentStream(doc, page, AppendMode.PREPEND, true, true);

Beware, though, in certain cases the image won't be visible in the background, e.g. if the existing content starts with an instruction to fill the whole page area in white. In such a case watermarks must be applied with some kind of transparency atop existing content.