<%@ page contentType="image/jpeg" import="java.awt.*,java.awt.image.*,com.sun.image.codec.jpeg.*,java.util.*" %>
<%!
Color getRandColor(int fc,int bc){//給定范圍獲得隨機(jī)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);
}
%>
<%


//設(shè)置頁(yè)面不緩存
response.setHeader("Pragma","No-cache");
response.setHeader("Cache-Control","no-cache");
response.setDateHeader("Expires", 0);

out.clear();


// 在內(nèi)存中創(chuàng)建圖象
int width=60, height=20;
BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);

// 獲取圖形上下文
Graphics g = image.getGraphics();

//生成隨機(jī)類(lèi)
Random random = new Random();

// 設(shè)定背景色
g.setColor(getRandColor(200,250));
g.fillRect(0, 0, width, height);

//設(shè)定字體
g.setFont(new Font("Times New Roman",Font.PLAIN,18));

//畫(huà)邊框
//g.setColor(new Color());
//g.drawRect(0,0,width-1,height-1);

// 隨機(jī)產(chǎn)生155條干擾線(xiàn)，使圖象中的認(rèn)證碼不易被其它程序探測(cè)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);
}

// 取隨機(jī)產(chǎn)生的認(rèn)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(rèn)證碼顯示到圖象中
g.setColor(new Color(20+random.nextInt(110),20+random.nextInt(110),20+random.nextInt(110)));//調(diào)用函數(shù)出來(lái)的顏色相同，可能是因?yàn)榉N子太接近，所以只能直接生成
g.drawString(rand,13*i+6,16);
}

// 將認(rèn)證碼存入SESSION
session.setAttribute("rand",sRand);

// 圖象生效
g.dispose();



// 輸出圖象到頁(yè)面
//ImageIO.write(image, "JPEG",response.getOutputStream());

ServletOutputStream outStream = response.getOutputStream();
JPEGImageEncoder encoder =JPEGCodec.createJPEGEncoder(outStream);
encoder.encode(image);
outStream.close();

//out.clear();
%>