// 
package app61;

import java.io.*;
import java.util.*;
import com.sun.image.codec.jpeg.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.awt.*;
import java.awt.image.*;

public class VerifyCode extends HttpServlet {

private Font mFont = new Font("Times New Roman", Font.PLAIN, 18); //設(shè)置字體

public void doGet(HttpServletRequest request, HttpServletResponse response) throws
ServletException, IOException {
//取得一個1000-9999的隨機數(shù)
 HttpSession session = request.getSession(true);
 response.setContentType("image/gif");
 response.setHeader("Pragma", "No-cache");
 response.setHeader("Cache-Control", "no-cache");
 response.setDateHeader("Expires", 0);
 int width = 60, height = 20;

 ServletOutputStream out = response.getOutputStream();
 BufferedImage image = new BufferedImage(width, height,
 BufferedImage.TYPE_INT_RGB); //設(shè)置圖片大小的
 Graphics gra = image.getGraphics();
 Random random = new Random();
 gra.setColor(getRandColor(200, 250)); //設(shè)置背景色rand墊底
 gra.fillRect(0, 0, width, height);
 gra.setColor(Color.black); //設(shè)置字體色
 gra.setFont(mFont);
 // 隨機產(chǎn)生155條干擾線，使圖象中的認證碼不易被其它程序探測到
 gra.setColor(getRandColor(160, 200));
 for (int i = 0; i < 155; i++) {
 int x = random.nextInt(width);
 int y = random.nextInt(height);
 int xl = random.nextInt(12);
 int yl = random.nextInt(12);
 gra.drawLine(x, y, x + xl, y + yl);
 }

 // 取隨機產(chǎn)生的認證碼(4位數(shù)字)
 String sRand = "";
 for (int i = 0; i < 4; i++) {
 String rand = String.valueOf(random.nextInt(10));
 sRand += rand;
 // 將認證碼顯示到圖象中
 gra.setColor(new Color(20 + random.nextInt(110),
 20 + random.nextInt(110),
 20 + random.nextInt(110))); //調(diào)用函數(shù)出來的顏色相同，可能是因為種子太接近，所以只能直接生成
 gra.drawString(rand, 13 * i + 6, 16);
 }
 session.setAttribute("rand",sRand);
 // session.setAttribute("getImg", sRand);
 JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out);
 encoder.encode(image);
 out.close();
}

static Color getRandColor(int fc, int bc) { //給定范圍獲得隨機顏色
 Random random = new Random();
 if (fc > 255)
 fc = 255;
 if (bc > 255)
 bc = 255;
 int r = fc + random.nextInt(bc - fc);
 int g = fc + random.nextInt(bc - fc);
 int b = fc + random.nextInt(bc - fc);
 return new Color(r, g, b);
}

 //Clean up resources
 public void destroy() {
 }
}