如何使用JAVA实现数字水印

package cumt.zry.two; 
 
import java.awt.*; 
import java.awt.image.BufferedImage; 
import java.io.*; 
import javax.imageio.*; 
 
public class Watermark2{ 
 public Watermark2(){super();}; 
/** 
 * 在源图片上设置水印文字 
 */ 
 public void WordsToImage(String srcImagePath,float alpha, 
   String font,int fontStyle,int fontSize,Color color, 
   String inputWords,int x,int y,String imageFormat,String toPath) throws IOException{ 
  FileOutputStream fos=null; 
  try { 
   //读取图片 
   BufferedImage image = ImageIO.read(new File(srcImagePath)); 
   //创建java2D对象 
   Graphics2D g2d=image.createGraphics(); 
   //用源图像填充背景 
   g2d.drawImage(image, 0, 0, image.getWidth(), image.getHeight(), null, null); 
    
   //!!!! 
   AlphaComposite ac = AlphaComposite.getInstance(AlphaComposite.SRC_OVER, alpha); 
   //为 Graphics2D 上下文设置 Composite。 Composite 用于所有绘制方法中，如 drawImage、 
   //drawString、draw 和 fill。 它指定新的像素如何在呈现过程中与图形设备上的现有像素组合。 
   g2d.setComposite(ac); 
    
   //设置文字字体名称、样式、大小 
   g2d.setFont(new Font(font, fontStyle, fontSize)); 
   g2d.setColor(color);//设置字体颜色 
   g2d.drawString(inputWords, x, y); //输入水印文字及其起始x、y坐标 
   g2d.dispose(); 
   //将水印后的图片写入toPath路径中 
   fos=new FileOutputStream(toPath); 
   ImageIO.write(image, imageFormat, fos); 
  } 
  //文件操作错误抛出 
  catch (Exception e) { 
   e.printStackTrace(); 
  }finally{ 
   if(fos!=null){ 
    fos.close(); 
   } 
  } 
 } 
  
 /** 
  * 在源图像上设置图片水印 
  */ 
 public void ImageToImage(String srcImagePath,String appendImagePath, 
   float alpha,int x,int y,int width,int height, 
   String imageFormat,String toPath) throws IOException{ 
   FileOutputStream fos = null; 
  try { 
   //读图 
   BufferedImage image = ImageIO.read(new File(srcImagePath)); 
   //创建java2D对象 
   Graphics2D g2d=image.createGraphics(); 
   //用源图像填充背景 
   g2d.drawImage(image, 0, 0, image.getWidth(), image.getHeight(), null, null); 
    
   //关键地方 
   AlphaComposite ac = AlphaComposite.getInstance(AlphaComposite.SRC_OVER, alpha); 
   g2d.setComposite(ac); 
    
   BufferedImage appendImage = ImageIO.read(new File(appendImagePath)); 
   g2d.drawImage(appendImage, x, y, width, height, null, null); 
   g2d.dispose(); 
   fos=new FileOutputStream(toPath); 
   ImageIO.write(image, imageFormat, fos); 
  } catch (Exception e) { 
   e.printStackTrace(); 
  }finally{ 
   if(fos!=null){ 
    fos.close(); 
   } 
  } 
 } 
  
 public static void main(String[] args) throws Exception 
 { 
  Watermark2 imageObj = new Watermark2(); 
  //源图片路径 
  String srcImagePath = "F:/27.jpg"; 
  //水印图片路径 
  String appendImagePath = "F:/logo.jpg"; 
  // ---- 宋体 普通字体 77号字 红色 透明度0.4" 
  float alpha = 0.4F; 
  String font = "宋体"; 
  int fontStyle = Font.PLAIN; 
  int fontSize = 77; 
  Color color = Color.RED; 
   
  String inputWords = "图片上设置水印文字"; 
  int x = 1700; 
  int y = 77; 
  String imageFormat = "jpg"; 
  //水印文字后的存储路径 
  String wToPath = "F:/31.png"; 
  //水印图片后的存储路径 
  String IToPath = "F:/7.png" ; 
  imageObj.WordsToImage(srcImagePath, alpha, font, fontStyle, 
    fontSize, color, inputWords, x, y, imageFormat, wToPath); 
  imageObj.ImageToImage(srcImagePath, appendImagePath, alpha, 
    x, y, 300, 200, imageFormat, IToPath); 
   
   
 } 
}