<%@ page language="java" contentType="image/jpeg"
??? pageEncoding="gb2312"%>
<%@ page import="java.awt.*,java.awt.image.*,java.util.*,javax.imageio.*"%>

<%!
?? Color getRandColor(int fc,int bc){
?Random rand=new Random();
?if(fc>255) fc=255;
?if(bc>255) bc=255;
?int r=fc+rand.nextInt(bc-fc);
?int g=fc+rand.nextInt(bc-fc);
?int b=fc+rand.nextInt(bc-fc);
?return new Color(r,g,b);
}
%>
<%
? //設置頁面不緩存
? response.setHeader("Pragma","No-cache");
? response.setHeader("Cache-Control","no-cache");
? response.setDateHeader("Expires",0);
?
? //在內存中創建圖像
? int width=60,height=20;
? BufferedImage image=new BufferedImage(width,height,BufferedImage.TYPE_INT_BGR);
?
? //獲取圖像
? Graphics g=image.getGraphics();
? //生成隨機類
? Random rand=new Random();
? //設定背景顏色
? g.setColor(getRandColor(200,250));
? g.fillRect(0,0,width,height);
? //設定字體
? g.setFont(new Font("Times New Roman",Font.PLAIN,18));
//隨機產生155條干擾線，使圖象中的認證碼不易被其它程序探測到
?g.setColor(getRandColor(160,200));
?for(int i=0;i<155;i++){
? int x=rand.nextInt(width);
? int y=rand.nextInt(height);
? int x1=rand.nextInt(12);
? int y1=rand.nextInt(12);
? g.drawLine(x,y,x+x1,y+y1);
?
?}
?//取隨機產生的4位驗證碼
?String sRand="";
?for(int i=0;i<4;i++){
? String strRand=String.valueOf(rand.nextInt(10));
? sRand+=strRand;
? //將驗證碼顯示到圖像中
? g.setColor(new Color(20+rand.nextInt(110),20+rand.nextInt(110),20+rand.nextInt(110)));
? g.drawString(strRand,13*i+6,16);

?}
?//將驗證碼放入session
? session.setAttribute("rand",sRand);
?
?g.dispose();
//輸出圖象到頁面
?ImageIO.write(image, "JPEG", response.getOutputStream());

?

%>