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【摘 要】
<%@?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.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(200,250));
g.fillRect(0,?0,?width,?height);
//设定字体
g.setFont(new?Font("Times?New?Roman",Font.PLAIN,18));
//画边框
g.setColor(new?Color(255,255,255));
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)
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+6,16);
}
//?将认证码存入SESSION
session.setAttribute("rand",sRand);
//?图象生效
g.dispose();
//?输出图象到页面
ImageIO.write(image,?"JPEG",?response.getOutputStream());
%>
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