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itext PDF文件打印水印
前言：公司有个需求，打印的合同模板要加上水印，但是由于itext版本问题，网上千篇一律的方法基本都没办法有效使用，然后自己琢磨下，记录下实现水印的功能的笔记。多页上都加上水印，核心就是加上自定义处理器实现水印功能.
PS: 这个也不是适用于itextpdf的所有版本，项目中引用的版本是： com.itextpdf:kernel:7.2.3，如其他版本不适用请自行调整代码
1.实现文字水印
实现的效果：水印加上透明度，不影响原先的内容，文字45度倾斜，文体是自定义字体，然后就是平铺真个整个页面。
TextWatermarkEventHandler
import com.itextpdf.kernel.colors.ColorConstants;
import com.itextpdf.kernel.events.Event;
import com.itextpdf.kernel.events.IEventHandler;
import com.itextpdf.kernel.events.PdfDocumentEvent;
import com.itextpdf.kernel.font.PdfFont;
import com.itextpdf.kernel.geom.Rectangle;
import com.itextpdf.kernel.pdf.PdfDocument;
import com.itextpdf.kernel.pdf.PdfPage;
import com.itextpdf.kernel.pdf.canvas.PdfCanvas;
import com.itextpdf.kernel.pdf.extgstate.PdfExtGState;
import lombok.extern.slf4j.Slf4j;@Slf4j
public class TextWatermarkEventHandler implements IEventHandler {private String watermarkText;private PdfFont font;private float fontSize;private static final float WIDTH_SPACING = 20;private static final float HEIGHT_SPACING = 130;private static final float ANGLE = 45;private static final float TRANSPARENCY = 0.3f;// 构造函数，传入水印文字、字体、大小、水平间距、垂直间距和旋转角度public TextWatermarkEventHandler(String text, PdfFont font, float fontSize) {this.watermarkText = text;this.font = font;this.fontSize = fontSize;}@Overridepublic void handleEvent(Event event) {PdfDocumentEvent docEvent = (PdfDocumentEvent) event;PdfDocument pdfDoc = docEvent.getDocument();PdfPage page = docEvent.getPage();// 获取页面大小Rectangle pageSize = page.getPageSize();PdfCanvas canvas = new PdfCanvas(page.newContentStreamBefore(), page.getResources(), pdfDoc);// 计算可用的页面宽度和高度float availableWidth = pageSize.getWidth();float availableHeight = pageSize.getHeight();// 创建图形状态并设置透明度PdfExtGState gState = new PdfExtGState();gState.setFillOpacity(TRANSPARENCY); // 设置透明度为 0.3// 文字的宽度float textWidth = font.getWidth(watermarkText, fontSize);// 调整初始绘制位置float startXOffset = -textWidth; // 从负数开始float startYOffset = -availableWidth; // 从负数开始// 绘制每一行水印文字for (float startY = startYOffset; startY < availableHeight + fontSize; startY += fontSize + HEIGHT_SPACING) {// 保存当前画布状态，确保透明度只影响水印canvas.saveState();// 设置透明度，仅影响水印canvas.setExtGState(gState);// 设置字体和大小canvas.setFontAndSize(font, fontSize);// 设置文字颜色（灰色水印）canvas.setFillColor(ColorConstants.LIGHT_GRAY);// 整行旋转canvas.concatMatrix((float) Math.cos(Math.toRadians(ANGLE)), (float) Math.sin(Math.toRadians(ANGLE)),(float) -Math.sin(Math.toRadians(ANGLE)), (float) Math.cos(Math.toRadians(ANGLE)),0, startY);// 绘制这一行的文字水印for (float x = startXOffset; x < availableWidth + textWidth; x += textWidth + WIDTH_SPACING) {canvas.beginText();canvas.moveText(x, 0);canvas.showText(watermarkText);canvas.endText();}// 恢复画布状态，确保透明度只影响水印canvas.restoreState();}// 释放画布资源canvas.release();}
}
调用TextWatermarkEventHandler监听器
// 自定义字体
String fontPath = WebUtils.getClasspath()+ File.separator+ "static" + File.separator + "font" + File.separator+"simsun.ttf";
PdfFont watermarkFont = PdfFontFactory.createFont(fontPath, PdfEncodings.IDENTITY_H, PdfFontFactory.EmbeddingStrategy.PREFER_EMBEDDED);
TextWatermarkEventHandler watermarkEventHandler = new TextWatermarkEventHandler("你是个大聪明呀",watermarkFont,30);
pdf.addEventHandler(PdfDocumentEvent.END_PAGE, watermarkEventHandler);
实现的效果(截取部分)
2.实现图片水印
实现的效果：水印加上透明度，不影响原先的内容，图片45度倾斜，图片进行缩放处理，然后就是平铺真个整个页面。（ps：此处的图片是经过缩放处理后的图片了）
ImageWatermarkEventHandler
import com.itextpdf.io.image.ImageData;
import com.itextpdf.io.image.ImageDataFactory;
import com.itextpdf.kernel.events.Event;
import com.itextpdf.kernel.events.IEventHandler;
import com.itextpdf.kernel.events.PdfDocumentEvent;
import com.itextpdf.kernel.geom.Rectangle;
import com.itextpdf.kernel.pdf.PdfDocument;
import com.itextpdf.kernel.pdf.PdfPage;
import com.itextpdf.kernel.pdf.canvas.PdfCanvas;
import com.itextpdf.kernel.pdf.extgstate.PdfExtGState;
import com.itextpdf.kernel.pdf.xobject.PdfImageXObject;
import lombok.extern.slf4j.Slf4j;@Slf4j
public class ImageWatermarkEventHandler implements IEventHandler {private String imagePath;private static final float SCALE = 1;private static final float WIDTH_SPACING = 20;private static final float HEIGHT_SPACING = 130;private static final float ANGLE = 45;private static final float TRANSPARENCY = 0.3f;// 构造函数，传入水印图片路径public ImageWatermarkEventHandler(String imagePath) {this.imagePath = imagePath;}@Overridepublic void handleEvent(Event event) {// 获取事件类型PdfDocumentEvent docEvent = (PdfDocumentEvent) event;PdfDocument pdfDoc = docEvent.getDocument();PdfPage page = docEvent.getPage();// 获取页面尺寸Rectangle pageSize = page.getPageSize();PdfCanvas canvas = new PdfCanvas(page.newContentStreamBefore(), page.getResources(), pdfDoc);ImageData imageData = null;try {imageData = ImageDataFactory.create(imagePath);PdfImageXObject watermarkImage = new PdfImageXObject(imageData);// 获取图片的原始宽高，按比例缩放float imgWidth = watermarkImage.getWidth() ;float imgHeight = watermarkImage.getHeight() ;// 计算可用的页面宽度和高度float availableWidth = pageSize.getWidth();
// float availableHeight = pageSize.getHeight();// 创建图形状态并设置透明度PdfExtGState gState = new PdfExtGState();gState.setFillOpacity(TRANSPARENCY); // 设置透明度为 0.3// 在页面上平铺水印图片for (float y = -availableWidth; y < pageSize.getHeight()*2; y += imgHeight + HEIGHT_SPACING) {for (float x = 0; x < pageSize.getWidth()*2; x += imgWidth + WIDTH_SPACING) {// 保存当前的画布状态canvas.saveState();// 设置水印的透明度canvas.setExtGState(gState);// 将图片水印旋转canvas.concatMatrix(Math.cos(Math.toRadians(ANGLE)),Math.sin(Math.toRadians(ANGLE)),-Math.sin(Math.toRadians(ANGLE)), Math.cos(Math.toRadians(ANGLE)),0, 0); // 旋转canvas.addXObjectAt(watermarkImage, x, y); // x, y 位置// 恢复画布状态canvas.restoreState();}}// 结束页面修改canvas.release();} catch (Exception e) {log.error("pdf添加水印报错:{}",e.getMessage());}}
}
调用TextWatermarkEventHandler监听器
String watermarkImagePath = WebUtils.getClasspath()+ File.separator+ "static" + File.separator + "image" + File.separator+"xxxx.jpg";
ImageWatermarkEventHandler watermarkEventHandler = new ImageWatermarkEventHandler(watermarkImagePath);
pdf.addEventHandler(PdfDocumentEvent.END_PAGE, watermarkEventHandler);
实现的效果(截取部分)
