一、需要用到的类

java.awt.image.BufferedImage;

javax.imageio.ImageIO;

java.io.*;

二、为什么要将BufferedImage转为byte数组

在传输中，图片是不能直接传的，因此需要把图片变为字节数组，然后传输比较方便；只需要一般输出流的write方法即可；

而字节数组变成BufferedImage能够还原图像；

三、如何取得BufferedImage

BufferedImage image = ImageIO.read(new File("1.gif"));

四、BufferedImage  ---->byte[]

ImageIO.write(BufferedImage image,String format,OutputStream out);方法可以很好的解决问题；

参数image表示获得的BufferedImage；

参数format表示图片的格式，比如“gif”等；

参数out表示输出流，如果要转成Byte数组，则输出流为ByteArrayOutputStream即可；

执行完后，只需要toByteArray()就能得到byte[];

五、byte[] ------>BufferedImage

ByteArrayInputStream in = new ByteArrayInputStream(byte[]b);    //将b作为输入流；

BufferedImage image = ImageIO.read(InputStream in);     //将in作为输入流，读取图片存入image中，而这里in可以为ByteArrayInputStream();

六、显示BufferedImage

public void paint(Graphics g){

super.paint(g);

g.drawImage(image,x,y,width,height,null);    //image为BufferedImage类型

}

如果要自动调用paint方法，则需要调用repaint()方法；

七、实例

要求：编写一个网络程序，通过Socket将图片从服务器端传到客户端，并存入文件系统；

Server端：

package org.exam3;

import java.awt.image.BufferedImage;
import java.io.ByteArrayOutputStream;
import java.io.DataOutputStream;
import java.io.File;
import java.net.ServerSocket;
import java.net.Socket;

import javax.imageio.ImageIO;

public class T6Server {

	public static void main(String[] args) throws Exception {
		ServerSocket server = new ServerSocket(8889);
		System.out.println("服务器开启连接...端口为8889");
		Socket s = server.accept();
		while(true){
			System.out.println("一客户端连接服务器，服务器传输图片...");
			DataOutputStream dout = new DataOutputStream(s.getOutputStream());
			BufferedImage image = ImageIO.read(new File("1.gif"));	//读取1.gif并传输
			ByteArrayOutputStream out = new ByteArrayOutputStream();
			boolean flag = ImageIO.write(image, "gif", out);
			byte[] b = out.toByteArray();
			dout.write(b);
			s.close();
			System.out.println("图片传送完毕,服务器开启连接...端口为8889");
			s = server.accept();
			
		}
	}
}

Client端：

package org.exam3;

import java.awt.BorderLayout;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.image.BufferedImage;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.DataInputStream;
import java.io.File;
import java.io.PrintWriter;
import java.net.Socket;

import javax.imageio.ImageIO;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;

public class T6Client extends JFrame {
	JButton button;
	JPanel panel;
	int count = 0;
	BufferedImage image ;
	public T6Client() {
		setSize(300, 400);
		button = new JButton("获取图像");
		add(button,BorderLayout.NORTH);
		button.addActionListener(new ActionListener() {
			public void actionPerformed(ActionEvent event) {
				try {
					Socket s = new Socket("localhost",8889);
					PrintWriter out = new PrintWriter(s.getOutputStream());
					out.print("a");
					DataInputStream in = new DataInputStream(s.getInputStream());
					byte[]b = new byte[1024];
					ByteArrayOutputStream bout = new ByteArrayOutputStream();
					int length = 0;
					while((length=in.read(b))!=-1){
						bout.write(b, 0, length);
					}
					ByteArrayInputStream bin = new ByteArrayInputStream(bout.toByteArray());
					image = ImageIO.read(bin);
					repaint();
					ImageIO.write(image, "gif", new File("output-"+count+".gif"));
					count++;
					s.close();
				} catch (Exception e) {
				}
			}
		});
		panel = new JPanel();
		add(panel);
	}
	@Override
	public void paint(Graphics g){
		super.paint(g);
		g.drawImage(image, 20, 20, 300, 150, null);//image为BufferedImage类型
	}
	public static void main(String[] args) throws Exception {
		T6Client frame = new T6Client();
		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		frame.setVisible(true);
	}

}