给pdf文件添加防伪水印logo（附工程源码下载）

<dependency>
    <groupId>com.itextpdf</groupId>
    <artifactId>itextpdf</artifactId>
    <version>5.5.3</version>
</dependency>

   
   

除了依赖以外，就一个类PDFAddWaterMark.Java了，其代码如下：

package com.luo.pdf;

import com.itextpdf.text.Image;
import com.itextpdf.text.pdf.PdfContentByte;
import com.itextpdf.text.pdf.PdfGState;
import com.itextpdf.text.pdf.PdfReader;
import com.itextpdf.text.pdf.PdfStamper;
import java.io.File;
import java.io.FileOutputStream;
import java.util.Random;

public class PDFAddWaterMark {

    static final float IAMGE_HEIGHT = 110f; // 限制水印图片的的高度
    static final float IAMGE_WIDTH = 110f; // 限制水印图片的的宽度

    /**
     * 给pdf文件添加水印
     * @param file 要加水印的原pdf文件
     * @throws Exception
     */
    public static void addPdfMark(File file) throws Exception {
        // 如果是web项目，应该从web项目里面获取logo
        // String markImagePath =
        // request.getSession().getServletContext().getRealPath("/") +
        // "resources/images/logo.jpg";
        String markImagePath = "C:/Users/luoguohui/Desktop/logo.jpg"; // 水印图片路径
        PdfReader reader = new PdfReader(file.getPath(), "PDF".getBytes());
        // 如果是web项目，直接下载应该放到response的流里面
        // PdfStamper stamp = new PdfStamper(reader,
        // response.getOutputStream());
        // 添加水印之后的pdf文件
        PdfStamper stamp = new PdfStamper(reader, new FileOutputStream(
                "C:/Users/luoguohui/Desktop/afterAddPdfMark.pdf"));
        int pageSize = reader.getNumberOfPages();

        float pageHeight = reader.getPageSize(1).getHeight();
        float pageWidth = reader.getPageSize(1).getWidth();
        try {
            // 每两行显示两个 左边一个，右边一个
            int lineNum = (int) (pageHeight / IAMGE_HEIGHT); // 行数
            int middleY = (int) pageWidth / 2;
            for (int i = 1; i <= pageSize; i++) {
                for (int j = 0, k = 0; j < lineNum; j = j + 2, k++) {
                    Random random = new Random();
                    Image img = Image.getInstance(markImagePath);// 插入水印
                    img.scaleAbsolute(IAMGE_WIDTH, IAMGE_HEIGHT * 184 / 455);
                    img.setAlignment(Image.UNDERLYING); // 在字下面
                    int trueY;
                    while (true) {
                        trueY = random.nextInt(middleY);
                        if (trueY > IAMGE_WIDTH / 2
                                && trueY < (middleY - IAMGE_WIDTH)) {
                            break;
                        }
                    }
                    img.setAbsolutePosition(trueY, j * IAMGE_HEIGHT
                            + (float) random.nextInt((int) IAMGE_HEIGHT)
                            - (k % 2) * 10); // 水印的位置
                    img.setRotationDegrees(random.nextInt(360));// 旋转 角度
                    PdfContentByte under = stamp.getUnderContent(i);
                    PdfGState gs = new PdfGState();
                    gs.setFillOpacity(0.3f); // 设置透明度为0.3
                    under.setGState(gs);
                    under.addImage(img);
                    while (true) {
                        trueY = random.nextInt(middleY) + middleY;
                        if (trueY > middleY + IAMGE_WIDTH / 2
                                && trueY < (2 * middleY - IAMGE_WIDTH)) {
                            break;
                        }
                    }
                    img.setAbsolutePosition(trueY, j * IAMGE_HEIGHT
                            + (float) random.nextInt((int) IAMGE_HEIGHT)
                            - (k % 2) * 10); // 水印的位置
                    img.setRotationDegrees(random.nextInt(360));// 旋转 角度
                    under.addImage(img);
                }
            }
        } catch (Exception e) {
            throw e;
        } finally {
            stamp.close();// 关闭
            reader.close();
        }

    }

    public static void main(String[] args) throws Exception {
        // 添加水印之前的pdf文件
        File file = new File("C:/Users/luoguohui/Desktop/beforeAddPdfMark.pdf");
        addPdfMark(file);
    }
}