<%@?page?contentType="image/jpeg"?import="java.awt.*,java.awt.image.*,java.util.*,javax.imageio.*"?%>
<%!
Color?getRandColor(int?fc,int?bc)...{//給定范圍獲得隨機顏色
????????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);
????????}
%>
<%
//設置頁面不緩存
response.setHeader("Pragma","No-cache");
response.setHeader("Cache-Control","no-cache");
response.setDateHeader("Expires",?0);

//?在內存中創建圖象
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();

//生成隨機類
Random?random?=?new?Random();

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

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

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


//?隨機產生155條干擾線，使圖象中的認證碼不易被其它程序探測到
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);
}

//?取隨機產生的認證碼(4位數字)
String?sRand="";
for?(int?i=0;i<4;i++)...{
????String?rand=String.valueOf(random.nextInt(10));
????sRand+=rand;
????//?將認證碼顯示到圖象中
????g.setColor(new?Color(20+random.nextInt(110),20+random.nextInt(110),20+random.nextInt(110)));//調用函數出來的顏色相同，可能是因為種子太接近，所以只能直接生成
????g.drawString(rand,13*i+6,16);
}

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


//?圖象生效
g.dispose();

//?輸出圖象到頁面
ImageIO.write(image,?"JPEG",?response.getOutputStream());
%>

?

轉載于:https://www.cnblogs.com/aijava/archive/2008/04/18/2191887.html

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