java - how to create watermark in PDF -

i have program generating money receipt organization. need add waterark in document sort of security. adding code below. pdf has been generating ok how add watermark?

/*  * change template, choose tools | templates  * , open template in editor.  */  package com.example;  import com.lowagie.text.*; import com.lowagie.text.pdf.*; import java.awt.color; import java.io.filenotfoundexception; import java.io.fileoutputstream;  /**  *  * @author chandan  */ public class moneryrecipt {     // document m_pdfdocument;       public static void main(string[] args) throws documentexception, filenotfoundexception     {               document m_pdfdocument = new document(pagesize.letter, 5, 5, 5, 5);     try    {        docwriter m_docwriter;    // pdfwriter m_pdfwriter = null;            pdfwriter writer =  pdfwriter.getinstance(m_pdfdocument, new fileoutputstream("e:/aa.pdf"));        image logo=image.getinstance("f:/gmc_report.jpg");       m_pdfdocument.open();       image background = image.getinstance(logo);       background.setabsoluteposition(200, 400);      // phrase watermarkdd = new phrase("chandan sarma", new font(fontfactory.getfont(fontfactory.helvetica, 20,font.normal,new color(240,240,240))));       pdfcontentbyte canvas = writer.getdirectcontentunder();       pdfcontentbyte addwatermark;       addwatermark=writer.getdirectcontentunder();       addwatermark.addimage(logo);           pdfptable maintable = new pdfptable(2);         pdfpcell spece = new pdfpcell();         spece.setborder(0);         spece.setcolspan(2);         spece.setfixedheight(20f);         spece.setspacecharratio(20f);         maintable.addcell(spece);          image logo=image.getinstance("d:/logo_gmcmanin.png");           paragraph ph = new paragraph();         ph.add(new chunk(logo, 0, 0));         ph.add(new chunk("\n\nguwahati municipal corporation", fontfactory.getfont(fontfactory.times_roman, 10, font.bolditalic)));         ph.add(new chunk("\n\nmoney recipt", fontfactory.getfont(fontfactory.times_roman, 10, font.bold)));          pdfpcell heading = new pdfpcell(ph);   //      heading.setborder(1);         heading.setcolspan(2);         heading.sethorizontalalignment(element.align_center);         heading.setverticalalignment(element.align_center);         maintable.addcell(heading);          paragraph ph2 = new paragraph();         ph2.add(new chunk("\npayment receipt / acknowledgment property tax bill of ", fontfactory.getfont(fontfactory.times_roman, 10, font.bolditalic)));         ph2.add(new chunk("\n\nfinancial year 2014-15", fontfactory.getfont(fontfactory.times_roman, 10, font.bold)));          pdfpcell reciptheading = new pdfpcell(ph2);   //      heading.setborder(1);         reciptheading.setcolspan(2);         reciptheading.sethorizontalalignment(element.align_center);         reciptheading.setverticalalignment(element.align_center);         maintable.addcell(reciptheading);          paragraph ph3 = new paragraph();         ph3.add(new chunk("receipt no  ", fontfactory.getfont(fontfactory.times_roman, 8, font.normal)));         ph3.add(new chunk(" 2014-15", fontfactory.getfont(fontfactory.times_roman, 8, font.normal)));          pdfpcell reciptcell=new pdfpcell(ph3);         //reciptcell.setborder(0);         //reciptcell.setborderwidthleft(1);         reciptcell.setborderwidthbottom(0);         reciptcell.setborderwidthtop(0);         reciptcell.setborderwidthright(0);         reciptcell.setcolspan(1);         reciptcell.sethorizontalalignment(element.align_center);         reciptcell.setverticalalignment(element.align_center);         maintable.addcell(reciptcell);          paragraph ph4 = new paragraph();         ph4.add(new chunk("date ", fontfactory.getfont(fontfactory.times_roman, 8, font.normal)));         ph4.add(new chunk("2014-15", fontfactory.getfont(fontfactory.times_roman, 8, font.normal)));          pdfpcell datecell=new pdfpcell(ph4);         datecell.setfixedheight(20);         //datecell.setborder(0);         datecell.setborderwidthleft(0);         datecell.setcolspan(1);         datecell.setborderwidthtop(0);         datecell.setborderwidthbottom(0);         datecell.sethorizontalalignment(element.align_center);         datecell.setverticalalignment(element.align_center);         maintable.addcell(datecell);           pdfpcell details = new pdfpcell();          //details.setborder(0);          details.setcolspan(2);           pdfptable detailstable = new pdfptable(2);         detailstable.setwidthpercentage(65);          pdfpcell ownercell=new pdfpcell(new phrase("owner’s name  ", fontfactory.getfont(fontfactory.times_roman, 8, font.normal)));         ownercell.sethorizontalalignment(element.align_left);         detailstable.addcell(ownercell);          pdfpcell ownernamecell=new pdfpcell(new phrase("chandan sarma ", fontfactory.getfont(fontfactory.times_roman, 8, font.normal)));         ownernamecell.sethorizontalalignment(element.align_right);         detailstable.addcell(ownernamecell);          pdfpcell assementidoldcell=new pdfpcell(new phrase("assessment id (old) ", fontfactory.getfont(fontfactory.times_roman, 8, font.normal)));         assementidoldcell.sethorizontalalignment(element.align_left);         detailstable.addcell(assementidoldcell);           pdfpcell assementidvaluecell=new pdfpcell(new phrase("27-05-7859 ", fontfactory.getfont(fontfactory.times_roman, 8, font.normal)));         assementidvaluecell.sethorizontalalignment(element.align_right);         detailstable.addcell(assementidvaluecell);           pdfpcell assementidnewcell=new pdfpcell(new phrase("assessment id (new) ", fontfactory.getfont(fontfactory.times_roman, 8, font.normal)));         assementidoldcell.sethorizontalalignment(element.align_left);         detailstable.addcell(assementidoldcell);          pdfpcell assementidnewvaluecell=new pdfpcell(new phrase("225642 ", fontfactory.getfont(fontfactory.times_roman, 8, font.normal)));         assementidnewvaluecell.sethorizontalalignment(element.align_right);         detailstable.addcell(assementidnewvaluecell);          details.setborderwidthtop(0);         details.setborderwidthbottom(0);         details.addelement(detailstable);         maintable.addcell(details);          paragraph ph6=new paragraph();         ph6.add(new chunk("household waste collection ", fontfactory.getfont(fontfactory.times_roman, 8, font.bolditalic,color.red)));         ph6.add(new chunk("\n\nward-wise contact number of ngos collecting household waste doorstep:- ", fontfactory.getfont(fontfactory.times_roman, 6)));         ph6.add(new chunk("\n\nward no. 1-   9957047867       ward no. 17- 9864623744", fontfactory.getfont(fontfactory.times_roman, 6)));         ph6.add(new chunk("\n\nward no. 1-   9957047867       ward no. 17- 9864623744", fontfactory.getfont(fontfactory.times_roman, 6)));         ph6.add(new chunk("\n\nward no. 1-   9957047867       ward no. 17- 9864623744", fontfactory.getfont(fontfactory.times_roman, 6)));         ph6.add(new chunk("\n\nward no. 1-   9957047867       ward no. 17- 9864623744", fontfactory.getfont(fontfactory.times_roman, 6)));         ph6.add(new chunk("\n\nward no. 1-   9957047867       ward no. 17- 9864623744", fontfactory.getfont(fontfactory.times_roman, 6)));         pdfpcell wastecollectionheader=new pdfpcell(ph6);         wastecollectionheader.setcolspan(1);         wastecollectionheader.sethorizontalalignment(element.align_center);         maintable.addcell(wastecollectionheader);          paragraph ph7=new paragraph();         ph7.add(new chunk("property tax related grievance redressal mechanism  ", fontfactory.getfont(fontfactory.times_roman, 8, font.bolditalic,color.red)));         ph7.add(new chunk("\n\nfor billing or service grievance, please approach (during office hours) ", fontfactory.getfont(fontfactory.times_roman, 6)));         ph7.add(new chunk("\n\n  •deputy commissioner, east zone, gmc, bhaya mama path, rg baruah road, mobile no: 07399092259 ", fontfactory.getfont(fontfactory.times_roman, 6)));         ph7.add(new chunk("\n\n  •deputy commissioner, east zone, gmc, bhaya mama path, rg baruah road, mobile no: 07399092259 ", fontfactory.getfont(fontfactory.times_roman, 6)));         ph7.add(new chunk("\n\n  •deputy commissioner, east zone, gmc, bhaya mama path, rg baruah road, mobile no: 07399092259 ", fontfactory.getfont(fontfactory.times_roman, 6)));         ph7.add(new chunk("\n\n  •deputy commissioner, east zone, gmc, bhaya mama path, rg baruah road, mobile no: 07399092259 ", fontfactory.getfont(fontfactory.times_roman, 6)));         ph7.add(new chunk("\n\n  •deputy commissioner, east zone, gmc, bhaya mama path, rg baruah road, mobile no: 07399092259 ", fontfactory.getfont(fontfactory.times_roman, 6)));          pdfpcell propertytexrelatedheader=new pdfpcell(ph7);         propertytexrelatedheader.setcolspan(1);         propertytexrelatedheader.sethorizontalalignment(element.align_center);         maintable.addcell(propertytexrelatedheader);               m_pdfdocument.add(maintable);         m_pdfdocument.newpage();         m_pdfdocument.setpagesize(m_pdfdocument.getpagesize());           m_pdfdocument.close();      }      catch(exception e)     {        system.out.println("exception is"+e.tostring());     }     } } 

add following lines of code when declaring pdf writer

pdfwriter writer =  pdfwriter.getinstance(m_pdfdocument, new fileoutputstream("d:/aa.pdf"));  m_pdfdocument.open(); phrase watermarkdd = new phrase("water mark name-", new font(fontfactory.getfont(fontfactory.helvetica, 20,font.normal,new color(240,240,240)))); pdfcontentbyte canvas = writer.getdirectcontentunder(); columntext.showtextaligned(canvas, element.align_center, watermarkdd, 298, 421, 45);  ----your remaining code goes here----------