php生成带干扰的验证码程序

php教程
/*
 * Created on 2011-3-11
 * Programmer : xiaoyao, QQ:1045195056
 验证通过判断输入值与$_SESSION['check_pic']值
 */
session_start();
 function RandAscii($number){//$number产生数字和字母个数
$arr=array('0','1','2','3','4','5','6','7','8','9',
'a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','w','v','u','x','y','z');
for ($i=1;$i<=$number;$i++)
{
$rand= $rand.$arr[rand(0,35)];
}
return $rand;
}
 $rand=RandAscii(4);

$_SESSION['check_pic']=$rand;//随机产生的四个数赋值session中，用于验证。
$x=80;
$y=24;
 $im=imagecreatetruecolor($x,$y);//创建图片
$bg=imagecolorallocate($im,255,255,255);//设置颜色背景
imagefill( $im,0,0,$bg);
$wh=imagecolorallocate($im,255,255,0);
$grey=imagecolorallocate($im,128,128,128);
$yellow=imagecolorallocate($im,255,255,0);
$red=imagecolorallocate($im,0,255,0);
$foregroundArr = array(imagecolorallocate($im, rand(0, 20), rand(0, 20), rand(0, 20)),
  imagecolorallocate($im, rand(0, 20), rand(0, 10), rand(245, 255)),
  imagecolorallocate($im, rand(245, 255), rand(0, 20), rand(0, 10)),
  imagecolorallocate($im, rand(245, 255), rand(0, 20), rand(245, 255))
 );//字颜色数组
 //画边框
 $border = imagecolorallocate($im, 133, 153, 193);
 imagerectangle($im, 0, 0, $x - 1, $y - 1, $border);

for($i=0;$i<10;$i++){        //画干扰线，10条
imageline($im,rand(0,60),2,rand(0,60),20,$yellow);

}
for($j=0;$j<100;$j++){
 imagesetpixel($im,rand()%76,rand()%20,$red);
}
//imagestring($im,6,15,8,$rand,$wh);//字体大小1-5
imagettftext($im, 14,rand(30, -30), 5, rand(15, 18) ,$foregroundArr[rand(0,3)], 'C:WindowsFontsArial.ttf',$rand[0]);
imagettftext($im, 14,rand(50, -50), 24, rand(15, 18),$foregroundArr[rand(0,3)], 'C:WindowsFontsArial.ttf',$rand[1]);
imagettftext($im, 14,rand(50, -50), 43, rand(15, 18) ,$foregroundArr[rand(0,3)], 'C:WindowsFontsArial.ttf',$rand[2]);
imagettftext($im, 14,rand(30, -30), 62, rand(15, 18),$foregroundArr[rand(0,3)], 'C:WindowsFontsArial.ttf',$rand[3]);

header("Content-type: image/jpeg");//输出图片
imagejpeg($im);
imagedestroy($im);
?>