求个验证码代码

[shuzai]

网上找到的,都是隐藏表单的做法...
谁有安全性高点的验证码代码,可以防那个什么ocr最好:D

[leyan728]

<?php
/***********************
* 文件名:authnum.php
* 作者:乐言(QQ:7928478)
* 主页:www.leyan.net
* 时间:2005-2-9
* 功能:图片验证吗
************************/
class activeCodeObj
{
function getCode ($length = 32, $mode = 0)
{
switch ($mode) {
case '1':
$str = '1234567890';
break;
case '2':
$str = 'abcdefghijklmnopqrstuvwxyz';
break;
case '3':
$str = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ';
break;
case '4':
$str = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz';
break;
case '5':
$str = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890';
break;
case '6':
$str = 'abcdefghijklmnopqrstuvwxyz1234567890';
break;
default:
$str = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz1234567890';
break;
}
$result='';
$l=strlen($str);
for($i=0;$i<$length;$i++){
$num = rand(0, $l);
$result .= $str[$num];
}
return $result;
}
}
$code = new activeCodeObj;
$authnum = $code->getCode(4,1);
//生成验证码图片
Header("Content-type: image/JPEG");
//srand((double)microtime()*1000000);
//建立空白图片
$im = imagecreate(50,20);
//为图片分配颜色
//黑色
$black = ImageColorAllocate($im, 0,0,0);
//白色
$white = ImageColorAllocate($im, 255,255,255);
//灰色
$gray = ImageColorAllocate($im, 200,200,200);
//红色
$red = imagecolorallocate($im, 255, 0, 0);
//将四位整数验证码绘入图片
imagestring($im, 5, 6, 3, $authnum, $white);
for($i=0;$i<200;$i++) //加入干扰象素
{
imagesetpixel($im, rand()%70, rand()%30, $gray);
}
ImageJPEG($im);
ImageDestroy($im);
?>