iText : How do I insert background image in the same document to be flushed to response

Question

I am creating a PDF and writing the stream in response. Before writing in the stream, I want to add a background image as watermark in all the pages so that PDF document flu

Answer 1

I have solved this with Bruno's second option. Here is the code.

public static String addBackgroundImageToPDF(ByteArrayOutputStream bos, String destPdfFileName, String templateImageFile)
{
  PdfReader sourcePDFReader = null;
  try
  {
        sourcePDFReader = new PdfReader(bos.toByteArray());
        int noOfPages = sourcePDFReader.getNumberOfPages();
        PdfStamper stamp = new PdfStamper(sourcePDFReader, new FileOutputStream(destPdfFileName));
        int i = 0;
        Image templateImage = Image.getInstance(templateImageFile);
        templateImage.setAbsolutePosition(0, 0);
        PdfContentByte tempalteBytes;
        while (i < noOfPages)
        {
              i++;
              tempalteBytes = stamp.getUnderContent(i);    
              tempalteBytes.addImage(templateImage);  
        }
         stamp.close();
        return destPdfFileName;
  }
  catch (Exception ex)
  {
        LOGGER.log(Level.INFO, "Error when applying template image as watermark");
  }
  finally
  {
        if (sourcePDFReader != null)
        {
              sourcePDFReader.close();
        }
  }
}

Answer 2

You can choose between two options:

1. Use the background image in a page event (to the 'under' content in the onEndPage() method)/
2. Create the first PDF in memory, then add the background image in a second pass using the code you posted.

I prefer option 1.

Answer 3

I solved this using Bruno's first (recommended) approach.

1) Create a page event helper with an onEndPage event:

class PDFBackground extends PdfPageEventHelper {

    @Override
    void onEndPage(PdfWriter writer, Document document) {
        Image background = Image.getInstance("myimage.png");
        // This scales the image to the page,
        // use the image's width & height if you don't want to scale.
        float width = document.getPageSize().getWidth();
        float height = document.getPageSize().getHeight();
        writer.getDirectContentUnder()
                .addImage(background, width, 0, 0, height, 0, 0);
    }

}

2) When creating your writer, register your page event helper:

PdfWriter writer = PdfWriter.getInstance(document, new FileOutputStream(file));
writer.setPageEvent(new PDFBackground());