给pdf加水印

package com.form.test;

import java.io.FileOutputStream;
import java.io.IOException;
 
import com.itextpdf.text.BaseColor;
import com.itextpdf.text.Chunk;
import com.itextpdf.text.Document;
import com.itextpdf.text.DocumentException;
import com.itextpdf.text.Element;
import com.itextpdf.text.Font;
import com.itextpdf.text.PageSize;
import com.itextpdf.text.Paragraph;
import com.itextpdf.text.Rectangle;
import com.itextpdf.text.pdf.BaseFont;
import com.itextpdf.text.pdf.PdfContentByte;
import com.itextpdf.text.pdf.PdfGState;
import com.itextpdf.text.pdf.PdfPCell;
import com.itextpdf.text.pdf.PdfPTable;
import com.itextpdf.text.pdf.PdfReader;
import com.itextpdf.text.pdf.PdfStamper;
import com.itextpdf.text.pdf.PdfWriter;
 
public class TestPriterWater {
  
    public static void main(String[] args) throws Exception {
        String pdfFilePath = "f:/itext-demo.pdf"; 
        PdfReader pdfReader = new PdfReader("/home/xueqy/1.pdf");
        // Get the PdfStamper object
        PdfStamper pdfStamper = new PdfStamper(pdfReader
            , new FileOutputStream(
                "/home/xueqy/2.pdf"));
        addWatermark(pdfStamper, "www.baidu.com");
 
        pdfStamper.close(); 
    }
 
     private static void addWatermark(PdfStamper pdfStamper
          , String waterMarkName) {
            PdfContentByte content = null;
            Rectangle pageRect = null;
            PdfGState gs = new PdfGState();
        
            try {
            	 BaseFont base = BaseFont.createFont();
                // 设置透明度为0.4
                gs.setFillOpacity(0.4f);
                gs.setStrokeOpacity(0.4f);
                int toPage = pdfStamper.getReader().getNumberOfPages();
              System.out.print(pdfStamper.getReader().getFileLength()+"    :" +toPage);  
                for (int i = 1; i <= toPage; i++) {
                    pageRect = pdfStamper.getReader().
                       getPageSizeWithRotation(i);
                    // 计算水印X,Y坐标
                    float x = pageRect.getWidth() / 2;
                    float y = pageRect.getHeight() / 2;
                    //获得PDF最顶层
                    content = pdfStamper.getOverContent(i);
                    content.saveState();
                    // set Transparency
                    content.setGState(gs);
                    content.beginText();
                    content.setColorFill(BaseColor.GRAY);
                    content.setFontAndSize(base, 24);
                  // content.setFontAndSize( 20);
                    content.showTextAligned(Element.ALIGN_CENTER
                            , waterMarkName, 300,
                            350, 30);
                    content.endText(); 
                }
            } catch (Exception ex) {
                ex.printStackTrace();
            } finally {
                content = null;
                pageRect = null;
            }
        }
 }