java实现图片加水印效果

import java.awt.AlphaComposite;
import java.awt.Color;
import java.awt.Font;
import java.awt.FontMetrics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.geom.AffineTransform;
import java.awt.image.BufferedImage;
import java.io.File;
import java.util.Iterator;

import javax.imageio.IIOImage;
import javax.imageio.ImageIO;
import javax.imageio.ImageReader;
import javax.imageio.ImageWriteParam;
import javax.imageio.ImageWriter;
import javax.imageio.stream.FileImageInputStream;
import javax.imageio.stream.FileImageOutputStream;

import org.junit.Test;

public class Wjt {

 @Test
 public void t3() throws Exception {
  File rootDir = new File("C:/Users/Administrator/Desktop/tem1");
  String[] fa = { "1.png", "2.jpg" };
  for (String s : fa) {
   String f = s;
   {
    FileImageInputStream fileImageInputStream = new FileImageInputStream(new File(rootDir, f));
    Iterator<ImageReader> imageReaders = ImageIO.getImageReaders(fileImageInputStream); //根据图片文件获取读取器
    ImageReader imageReader = imageReaders.hasNext() ? imageReaders.next() : null; //检测读取器是否存在
    imageReader.setInput(fileImageInputStream); //设置读取器输入流
    BufferedImage bufferedImage = imageReader.read(0); //从读取器取BufferedImage，这里只有一个，所以可以直接写0
    { //开始加水印
     Graphics2D graphics2d = bufferedImage.createGraphics(); //取画笔
     graphics2d.setRenderingHint(RenderingHints.KEY_TEXT_ANTIALIASING, RenderingHints.VALUE_TEXT_ANTIALIAS_ON); //设置画笔文字抗锯齿
     graphics2d.transform(AffineTransform.getTranslateInstance(bufferedImage.getWidth() / 2, bufferedImage.getHeight() / 2)); //将画笔移动到图片中央
     graphics2d.transform(AffineTransform.getRotateInstance(Math.toRadians(45))); //将画笔旋转一定弧度
     float radius = Double.valueOf(Math.sqrt(bufferedImage.getWidth() * bufferedImage.getWidth() + bufferedImage.getHeight() * bufferedImage.getHeight()) / 2).floatValue(); //计算图片外切圆半径
     Font waterMarkerFont = new Font("微软雅黑", Font.PLAIN, bufferedImage.getHeight() / 25); //设置画笔要用的字体，这里可以设置字体样式和大小
     graphics2d.setFont(waterMarkerFont); //设置画笔字体
     graphics2d.setColor(Color.WHITE); //设置画笔颜色
     graphics2d.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_ATOP, 0.3F)); //设置画笔操作透明度
     FontMetrics fontMetrics = graphics2d.getFontMetrics(); //取画笔字体信息
     String waterMarker = "THIS IS WATERMARK."; //水印文字
     int stringWidth = fontMetrics.stringWidth(waterMarker); //计算水印文字宽度，很多人卡在了这一步
     for (float i = -radius; i <= radius; i += (stringWidth + bufferedImage.getHeight() / 25)) { //循环添加水印，这里可以设置水印水平距离，单位：px
      for (float j = -radius; j <= radius; j += (fontMetrics.getHeight() + bufferedImage.getHeight() / 25)) { //这里可以设置水印垂直距离，单位：px
       graphics2d.drawString(waterMarker, i, j); //画水印
      }
     }
     graphics2d.dispose(); //释放画笔资源
    }
    ImageWriter imageWriter = ImageIO.getImageWriter(imageReader); //根据图片文件读取器获取图片文件写入器
    String[] split = f.split("\\.");
    FileImageOutputStream fileOutputStream = new FileImageOutputStream(new File(rootDir, split[0] + "r." + split[1])); //生成目标图片文件路径
    imageWriter.setOutput(fileOutputStream); //设置写入器输出流
    IIOImage iioImage = new IIOImage(bufferedImage, null, null);
    ImageWriteParam imageWriteParam = imageWriter.getDefaultWriteParam();
    if (imageReader.getFormatName().equals("JPEG")) { //jpg格式图片可设置输出图片文件的质量
     imageWriteParam.setCompressionMode(ImageWriteParam.MODE_EXPLICIT); //这一行固定这样写，跟下一行搭配
     imageWriteParam.setCompressionQuality(0.947F); //跟上一行搭配，设置输出图片文件的质量     
    }
    imageWriter.write(null, iioImage, imageWriteParam); //写文件
    imageWriter.dispose(); //关闭写入器
    imageReader.dispose(); //关闭读取器
   }
  }
 }
}