一、需要用到的类
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);
- }
- }
