图片添加水印（Java 实现）

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某些应用场景下需要对图片加上水印防止盗用，例如微博用户图片。Java中实现添加水印需要用到BufferedImage、Graphics2D 和ImageIO类。

1. 添加文字水印

import java.awt.AlphaComposite;
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics2D;
import java.awt.Image;
import java.awt.RenderingHints;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.FileOutputStream;
import java.io.OutputStream;
import javax.imageio.ImageIO;

/**
 * 添加文字水印
 *
 * @author Ricky Fung
 */
public class TextMarkProcessor {

    /**
     * @param args
     */
    public static void main(String[] args) {

        new TextMarkProcessor().testTextMark();
    }

    public void testTextMark() {
        File srcImgFile = new File("D:/test/desktop.png");
        String logoText = "[ 天使的翅膀 ]";

        File outputRotateImageFile = new File("D:/test/desktop_text_mark.jpg");

        createWaterMarkByText(srcImgFile, logoText, outputRotateImageFile, 0);
    }

    public void createWaterMarkByText(File srcImgFile, String logoText,
                                             File outputImageFile, double degree) {
        OutputStream os = null;
        try {
            Image srcImg = ImageIO.read(srcImgFile);

            BufferedImage buffImg = new BufferedImage(srcImg.getWidth(null),
                    srcImg.getHeight(null), BufferedImage.TYPE_INT_RGB);

            Graphics2D graphics = buffImg.createGraphics();
            graphics.setRenderingHint(RenderingHints.KEY_INTERPOLATION,
                    RenderingHints.VALUE_INTERPOLATION_BILINEAR);
            graphics.drawImage(srcImg.getScaledInstance(srcImg.getWidth(null),
                            srcImg.getHeight(null), Image.SCALE_SMOOTH), 0, 0, null);

            if (degree>0) {
                graphics.rotate(Math.toRadians(degree),
                        (double) buffImg.getWidth() / 2,
                        (double) buffImg.getHeight() / 2);
            }
            graphics.setColor(Color.RED);
            graphics.setFont(new Font("宋体", Font.BOLD, 36));

            float alpha = 0.8f;
            graphics.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_ATOP,
                    alpha));

            graphics.drawString(logoText, buffImg.getWidth()/3, buffImg.getHeight()/2);
            graphics.dispose();

            os = new FileOutputStream(outputImageFile);
            // 生成图片
            ImageIO.write(buffImg, "JPG", os);
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                if (null != os)
                    os.close();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }
}

2. 添加图片水印

import java.awt.AlphaComposite;
import java.awt.Graphics2D;
import java.awt.Image;
import java.awt.RenderingHints;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.FileOutputStream;
import java.io.OutputStream;
import javax.imageio.ImageIO;
import javax.swing.ImageIcon;

/**
 * 添加图片水印
 *
 * @author Ricky Fung
 */
public class PictureMarkProcessor {

    /**
     * @param args
     */
    public static void main(String[] args) {

        new PictureMarkProcessor().testPictureMark();
    }

    public void testPictureMark() {

        File srcImageFile = new File("D:/test/desktop.png");
        File logoImageFile = new File("D:/test/tools.png");

        File outputRoateImageFile = new File("D:/test/desktop_pic_mark.jpg");

        createWaterMarkByIcon(srcImageFile, logoImageFile, outputRoateImageFile, 0);
    }

    public void createWaterMarkByIcon(File srcImageFile, File logoImageFile,
                                             File outputImageFile, double degree) {

        OutputStream os = null;
        try {
            Image srcImg = ImageIO.read(srcImageFile);

            BufferedImage buffImg = new BufferedImage(srcImg.getWidth(null),
                    srcImg.getHeight(null), BufferedImage.TYPE_INT_RGB);

            Graphics2D graphics = buffImg.createGraphics();
            graphics.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BILINEAR);
            graphics.drawImage(srcImg.getScaledInstance(srcImg.getWidth(null),
                            srcImg.getHeight(null), Image.SCALE_SMOOTH), 0, 0, null);

            ImageIcon logoImgIcon = new ImageIcon(ImageIO.read(logoImageFile));
            Image logoImg = logoImgIcon.getImage();

            //旋转
            if (degree>0) {
                graphics.rotate(Math.toRadians(degree),
                        (double) buffImg.getWidth() / 2,
                        (double) buffImg.getWidth() / 2);
            }

            float alpha = 0.8f; // 透明度
            graphics.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_ATOP, alpha));

            //水印 的位置
            graphics.drawImage(logoImg, buffImg.getWidth()/3, buffImg.getHeight()/2, null);
            graphics.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_OVER));
            graphics.dispose();

            os = new FileOutputStream(outputImageFile);
            // 生成图片
            ImageIO.write(buffImg, "JPG", os);
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                if (null != os)
                    os.close();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }
}

实现效果如下：

原图：

加文字水印：

加图片水印：