花

<% @?page?contentType? = ? " ?image/jpeg " ? import = " java.awt.*? " ? %>
<% @?page? import ? = ? " 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());
%>