/**
* This will overlay two documents onto each other. The overlay document is repeatedly overlayed
* onto the destination document for every page in the destination.
*
* @param overlay The document to copy onto the destination
* @param destination The file that the overlay should be placed on.
* @return The destination pdf, same as argument passed in.
* @throws IOException If there is an error accessing data.
*/
public PDDocument overlay(PDDocument overlay, PDDocument destination) throws IOException {
pdfOverlay = overlay;
pdfDocument = destination;
PDDocumentCatalog overlayCatalog = pdfOverlay.getDocumentCatalog();
collectLayoutPages(overlayCatalog.getAllPages());
COSDictionary saveGraphicsStateDic = new COSDictionary();
saveGraphicsStateStream =
new COSStream(saveGraphicsStateDic, pdfDocument.getDocument().getScratchFile());
OutputStream saveStream = saveGraphicsStateStream.createUnfilteredStream();
saveStream.write(" q\n".getBytes("ISO-8859-1"));
saveStream.flush();
restoreGraphicsStateStream =
new COSStream(saveGraphicsStateDic, pdfDocument.getDocument().getScratchFile());
OutputStream restoreStream = restoreGraphicsStateStream.createUnfilteredStream();
restoreStream.write(" Q\n".getBytes("ISO-8859-1"));
restoreStream.flush();
PDDocumentCatalog pdfCatalog = pdfDocument.getDocumentCatalog();
processPages(pdfCatalog.getAllPages());
return pdfDocument;
}
