Java中PDF添加水印

在 PDF 中添加水印需要依赖 http://www.itextpdf.com/ 提供的 jar 包，我们新建 maven 项目，依赖如下：

<dependency>
            <groupId>com.itextpdf</groupId>
            <artifactId>itextpdf</artifactId>
            <version>5.5.13.2</version>
        </dependency>
        <dependency>
            <groupId>com.itextpdf</groupId>
            <artifactId>itext-asian</artifactId>
            <version>5.2.0</version>
</dependency>

代码结构如下：

PdfWaterMarkUtil

package net.haicoder.watermark;
import com.itextpdf.text.Element;
import com.itextpdf.text.Rectangle;
import com.itextpdf.text.pdf.*;
import javax.swing.*;
import java.awt.*;
import java.io.FileOutputStream;
/**
 * @author 嗨客网
 * @description pdf 支持水印
 */
public class PdfWaterMarkUtil {
    private static int interval = -5;
    /**
     * @param filePath         你的PDF文件地址
     * @param outputFile       添加水印后生成PDF存放的地址
     * @param waterMarkContent 你的水印
     * @return
     */
    public static boolean pdfWaterMark(String filePath, String outputFile, String waterMarkContent) {
        try {
            PdfReader reader = new PdfReader(filePath);
            PdfStamper stamper = new PdfStamper(reader, new FileOutputStream(outputFile));
            //这里的字体设置比较关键，这个设置是支持中文的写法
            BaseFont base = BaseFont.createFont("STSong-Light", "UniGB-UCS2-H", BaseFont.NOT_EMBEDDED);// 使用系统字体
            PdfGState gs = new PdfGState();
            gs.setFillOpacity(0.3f);
            gs.setStrokeOpacity(0.4f);
            int total = reader.getNumberOfPages() + 1;
            JLabel label = new JLabel();
            FontMetrics metrics;
            label.setText(waterMarkContent);
            metrics = label.getFontMetrics(label.getFont());
            int textH = metrics.getHeight();
            int textW = metrics.stringWidth(label.getText());
            PdfContentByte under;
            Rectangle pageRect;
            for (int i = 1; i < total; i++) {
                pageRect = reader.getPageSizeWithRotation(i);
                under = stamper.getOverContent(i);
                under.saveState();
                under.setGState(gs);
                under.beginText();
                under.setFontAndSize(base, 22);
                // 水印文字成30度角倾斜
                //你可以随心所欲的改你自己想要的角度
                for (int height = interval + textH; height < pageRect.getHeight(); height = height + textH * 10) {
                    for (int width = textW + 20; width < pageRect.getWidth() + textW; width = width + textW * 3) {
                        under.showTextAligned(Element.ALIGN_LEFT, waterMarkContent, width - textW, height, 30);
                    }
                }
                // 添加水印文字
                under.endText();
            }
            stamper.close();
            reader.close();
            return true;
        } catch (Exception e) {
            e.printStackTrace();
            return false;
        }
    }
}

测试类

import net.haicoder.watermark.PdfWaterMarkUtil;
/**
 * @author 嗨客网
 * @description
 */
public class TestMain {
    public static void main(String[] args) {
        PdfWaterMarkUtil.pdfWaterMark("/Users/haicoder/Documents/code/haicoder/javautil/src/main/java/图片添加水印.pdf",
                "/Users/haicoder/Documents/code/haicoder/javautil/src/main/java/图片添加水印1.pdf",
                "你好，嗨客网");
    }
}

运行效果如下：