把图片背景［白色］设置透明

package com.goldgrid.socket.client;

import java.awt.Graphics2D;
import java.awt.Image;
import java.awt.image.BufferedImage;
import java.io.ByteArrayOutputStream;
import java.io.File;

import javax.imageio.ImageIO;
import javax.swing.ImageIcon;

import org.apache.log4j.Logger;

public class Alpha {
 
    protected static Logger logger = Logger.getLogger(ClientSocket.class);

 public byte[] transferAlpha(Image image) {

  ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();

  try {
   ImageIcon imageIcon = new ImageIcon(image);
   BufferedImage bufferedImage = new BufferedImage(imageIcon
     .getIconWidth(), imageIcon.getIconHeight(),
     BufferedImage.TYPE_4BYTE_ABGR);
   Graphics2D g2D = (Graphics2D) bufferedImage.getGraphics();
   g2D.drawImage(imageIcon.getImage(), 0, 0, imageIcon
     .getImageObserver());
   int alpha = 0;
   for (int j1 = bufferedImage.getMinY(); j1 < bufferedImage
     .getHeight(); j1++) {
    for (int j2 = bufferedImage.getMinX(); j2 < bufferedImage
      .getWidth(); j2++) {
     int rgb = bufferedImage.getRGB(j2, j1);
    
     int R =(rgb & 0xff0000 ) >> 16 ;
     int G= (rgb & 0xff00 ) >> 8 ;
     int B= (rgb & 0xff );
     if(((255-R)<30) && ((255-G)<30) && ((255-B)<30)){
      rgb = ((alpha + 1) << 24) | (rgb & 0x00ffffff);
     }

     bufferedImage.setRGB(j2, j1, rgb);

    }
   }

   g2D.drawImage(bufferedImage, 0, 0, imageIcon.getImageObserver());
   //ImageIO.write(bufferedImage, "png", new File("d:/test.png.png"));

   ImageIO.write(bufferedImage, "png", byteArrayOutputStream);
  } catch (Exception e) {
   logger.error(e.toString());
  }finally{
   
  }

  return byteArrayOutputStream.toByteArray();

 }
}