当前位置：首页 > Java

java如何加水印

2026-03-22 23:35:14Java

添加水印的方法

使用Java的Graphics2D类 通过Graphics2D绘制文本或图像水印到目标图片上。以下是核心代码示例：

import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.File;
import javax.imageio.ImageIO;

public class Watermark {
    public static void addTextWatermark(File inputFile, File outputFile, String text) throws Exception {
        BufferedImage image = ImageIO.read(inputFile);
        Graphics2D g2d = (Graphics2D) image.getGraphics();

        // 设置字体和颜色
        g2d.setFont(new Font("Arial", Font.BOLD, 30));
        g2d.setColor(Color.RED);

        // 计算水印位置（居中）
        FontMetrics metrics = g2d.getFontMetrics();
        int x = (image.getWidth() - metrics.stringWidth(text)) / 2;
        int y = (image.getHeight() - metrics.getHeight()) / 2 + metrics.getAscent();

        // 绘制水印
        g2d.drawString(text, x, y);
        g2d.dispose();

        ImageIO.write(image, "png", outputFile);
    }
}

使用透明图像水印 加载PNG格式的透明水印图片，叠加到目标图像上：

public static void addImageWatermark(File inputFile, File watermarkFile, File outputFile) throws Exception {
    BufferedImage image = ImageIO.read(inputFile);
    BufferedImage watermark = ImageIO.read(watermarkFile);

    Graphics2D g2d = (Graphics2D) image.getGraphics();
    g2d.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_OVER, 0.5f)); // 设置透明度
    g2d.drawImage(watermark, image.getWidth() - watermark.getWidth() - 10, 
                  image.getHeight() - watermark.getHeight() - 10, null);
    g2d.dispose();

    ImageIO.write(image, "png", outputFile);
}

进阶处理技巧

旋转水印 通过AffineTransform实现倾斜水印效果：

Graphics2D g2d = (Graphics2D) image.getGraphics();
AffineTransform at = new AffineTransform();
at.rotate(Math.toRadians(-45)); // 旋转45度
g2d.setTransform(at);
g2d.drawString("Watermark", x, y);

平铺水印 使用循环在图像上重复绘制水印：

java如何加水印

for (int x = 0; x < image.getWidth(); x += watermark.getWidth() + 50) {
    for (int y = 0; y < image.getHeight(); y += watermark.getHeight() + 50) {
        g2d.drawImage(watermark, x, y, null);
    }
}