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<%@ page language="java" pageEncoding="GBK"%>
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<%@ include file="../common/taglibs.jsp"%>
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<%@ page contentType="image/jpeg" import="java.awt.*,java.awt.image.*,com.sun.image.codec.jpeg.*,java.util.*" %>
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<%!
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Color getRandColor(int fc,int bc){//给定范围获得随机颜色
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Random random = new Random();
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if(fc>255) fc=255;
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if(bc>255) bc=255;
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int r=fc+random.nextInt(bc-fc);
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int g=fc+random.nextInt(bc-fc);
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int b=fc+random.nextInt(bc-fc);
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return new Color(r,g,b);
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}
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%>
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<%
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//设置页面不缓存
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response.setHeader("Pragma","No-cache");
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response.setHeader("Cache-Control","no-cache");
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response.setDateHeader("Expires", 0);
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out.clear();
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// 在内存中创建图象
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int width=60, height=20;
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BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
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// 获取图形上下文
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Graphics g = image.getGraphics();
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//生成随机类
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Random random = new Random();
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// 设定背景色
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g.setColor(getRandColor(200,250));
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g.fillRect(0, 0, width, height);
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//设定字体
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g.setFont(new Font("Times New Roman",Font.PLAIN,18));
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//画边框
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//g.setColor(new Color());
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//g.drawRect(0,0,width-1,height-1);
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// 随机产生155条干扰线，使图象中的认证码不易被其它程序探测到
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g.setColor(getRandColor(160,200));
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for (int i=0;i<155;i++)
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{
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int x = random.nextInt(width);
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int y = random.nextInt(height);
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int xl = random.nextInt(12);
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int yl = random.nextInt(12);
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g.drawLine(x,y,x+xl,y+yl);
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}
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// 取随机产生的认证码(4位数字)
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String sRand="";
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for (int i=0;i<4;i++){
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String rand=String.valueOf(random.nextInt(10));
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sRand+=rand;
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// 将认证码显示到图象中
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g.setColor(new Color(20+random.nextInt(110),20+random.nextInt(110),20+random.nextInt(110)));//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
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g.drawString(rand,13*i+6,16);
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}
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// 将认证码存入SESSION
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session.setAttribute("rand",sRand);
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// 图象生效
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g.dispose();
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// 输出图象到页面
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//ImageIO.write(image, "JPEG",response.getOutputStream());
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ServletOutputStream outStream = response.getOutputStream();
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JPEGImageEncoder encoder =JPEGCodec.createJPEGEncoder(outStream);
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encoder.encode(image);
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outStream.close();
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//out.clear();
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%>
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