制作验证码

<%@ page contentType="image/jpeg" import="java.awt.*,java.awt.image.*,java.util.*,javax.imageio.*" %>
<%!
  Color getRandColor(int fc,int bc){//给定范围获得随机颜色
         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);
         }
%>
<%
 //设置页面不缓存
  response.reset();
                out.clear();
  response.setHeader("Pragma", "No-cache");
  response.setHeader("Cache-Control", "no-cache");
  response.setDateHeader("Expires", 0);
  // 在内存中创建图象
  int width = 60, height = 20;
  BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
  // 获取图形上下文
  Graphics g = image.getGraphics();
  //生成随机类
  Random random = new Random();
  // 设定背景色
  g.setColor(getRandColor(240, 250));
  g.fillRect(0, 0, width, height);
  //设定字体
  g.setFont(new Font("Times New Roman", Font.BOLD, 18));
  //画边框
  //g.setColor(new Color());
  //g.drawRect(0,0,width-1,height-1);
  // 随机产生10条干扰线，使图象中的认证码不易被其它程序探测到
  g.setColor(getRandColor(150, 200));
  for (int i = 0; i < 10; i++) {
   int x = random.nextInt(width);
   int y = random.nextInt(height);
   int xl = random.nextInt(12);
   int yl = random.nextInt(12);
   g.drawLine(x, y, x + xl, y + yl);
  }
  // 取随机产生的认证码(4位数字)
  String sRand = "";
  for (int i = 0; i < 4; i++) {
   String rand = String.valueOf(random.nextInt(10));
   //性能测试专用
   //rand="1";
   sRand += rand;
   // 将认证码显示到图象中
   g.setColor(new Color(20 + random.nextInt(150), 20 + random.nextInt(150), 20 + random.nextInt(150)));
   //调用函数出来的颜色相同，可能是因为种子太接近，所以只能直接生成
   g.drawString(rand, 14 * i + 6, 16);
  }
  // 将认证码存入SESSION
  session.setAttribute("verify", sRand);
  // 图象生效
  g.dispose();
  // 输出图象到页面
  ImageIO.write(image, "JPEG", response.getOutputStream());
%>