<%@page import="java.awt.*,java.awt.image.*,java.util.*,javax.imageio.*, sun.misc.BASE64Encoder, java.awt.image.DataBufferByte, java.io.*,javax.swing.ImageIcon"%>

//tomcat下 
<%@ page contentType="image/jpg"  language="java"%>

//resin下
<%@ page contentType="text/html"  language="java"%>

<%!
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);
}
%>
<%
out.clear();

//设置页面不缓存
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=30;
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(200,250)); 
g.fillRect(0, 0, width, height);

//设定字体
g.setFont(new Font("Times New Roman",Font.PLAIN, 32));

//画边框
//g.setColor(new Color());
//g.drawRect(0,0,width-1,height-1);


// 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
g.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);
        g.drawLine(x,y,x+xl,y+yl);
}

// 取随机产生的认证码(4位数字)
/*
for(int i=0; i < sRand.length(); i++) {
    String rand=String.valueOf(sRand.charAt(i));
    // 将认证码显示到图象中
    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
    g.drawString(rand, 13*i + 6, 16);
}
*/

String sRand = "";
for (int i=0;i<4;i++){
    String rand=String.valueOf(random.nextInt(10));
    sRand+=rand;
    // 将认证码显示到图象中
    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
    g.drawString(rand, 13*i+2, 24);
}


// 将认证码存入SESSION
session.setAttribute("validateCode", sRand);

// 图象生效
g.dispose();

// tomcat下使用下方法输出图象到页面
//ImageIO.write(image, "JPG", response.getOutputStream());

//resin 下base64解决办法
ByteArrayOutputStream byteOut = new ByteArrayOutputStream(); 
try {
    ImageIO.write(image, "JPEG", byteOut);
    
    byte[] data = byteOut.toByteArray(); 
    
    BASE64Encoder encoder = new BASE64Encoder();
    out.write(encoder.encode(data));

    out.flush();
    out.clear();
} catch (IOException e) { 
    e.printStackTrace();
}

%>