php图片验证码代码

session_start();
session_register('safecode');
$type = 'gif';
$width= 40;
$height= 16;
header("content-type: image/".$type);
srand((double)microtime()*1000000);
$randval = randstr(4,"");
if($type!='gif' && function_exists('imagecreatetruecolor')){
     $im = @imagecreatetruecolor($width,$height);
}else{
     $im = @imagecreate($width,$height);
}
     $r = array(225,211,255,223);
     $g = array(225,236,237,215);
     $b = array(225,236,166,125);

     $key = rand(0,3);
 
     $backcolor = imagecolorallocate($im,$r[$key],$g[$key],$b[$key]);//背景色（随机）
     $bordercolor = imagecolorallocate($im, 0, 0, 0);//边框色
     $pointcolor = imagecolorallocate($im, 255, 170, 255);//点颜色

     @imagefilledrectangle($im, 0, 0, $width - 1, $height - 1, $backcolor);//背景位置
     @imagerectangle($im, 0, 0, $width-1, $height-1, $bordercolor); //边框位置
     $stringcolor = imagecolorallocate($im, 255,51,153);

     for($i=0;$i<=100;$i++){
           $pointx = rand(2,$width-2);
           $pointy = rand(2,$height-2);
           @imagesetpixel($im, $pointx, $pointy, $pointcolor);
     }

     @imagestring($im, 3, 5, 1, $randval, $stringcolor);
     $imagefun='image'.$type;
     $imagefun($im);
     @imagedestroy($im);
     $_session['safecode'] = $randval;
//产生随机字符串
function randstr($len=6,$format='all') {
           switch($format) {
                 case 'all':
                 $chars='abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz0123456789www.111com.net'; break;
                 case 'char':
                 $chars='abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz'; break;
                 case 'number':
                 $chars='0123456789'; break;
                 default :
                 $chars='abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz0123456789';
                 break;
           }
     $string="";
     while(strlen($string)<$len)
     $string.=substr($chars,(mt_rand()%strlen($chars)),1);
     return $string;
}

//调用此页面，如果下面的式子成立，则生成验证码图片
if($_get["action"]=="verifycode")
{
    rand_create();
}
//验证码图片生成
function rand_create()
{
    //通知浏览器将要输出png图片
    header("content-type: image/png");
    //准备好随机数发生器种子 
    srand((double)microtime()*1000000);
    //准备图片的相关参数  
    $im = imagecreate(62,20);
    $black = imagecolorallocate($im, 0,0,0);  //rgb黑色标识符
    $white = imagecolorallocate($im, 255,255,255); //rgb白色标识符
    $gray = imagecolorallocate($im, 200,200,200); //rgb灰色标识符
    //开始作图    
    imagefill($im,0,0,$gray);
    while(($randval=rand()%100000)<10000);{
        $_session["login_check_num"] = $randval;
        //将四位整数验证码绘入图片 
        imagestring($im, 5, 10, 3, $randval, $black);
    }
    //加入干扰象素   
    for($i=0;$i<200;$i++){
        $randcolor = imagecolorallocate($im,rand(0,255),rand(0,255),rand(0,255));
        imagesetpixel($im, rand()%70 , rand()%30 , $randcolor);
    }
    //输出验证图片
    imagepng($im);
    //销毁图像标识符
    imagedestroy($im);
}
//检验验证码
function rand_check()
{
    if($_post["reg_rand"] == $_session["login_check_num"]){
        return true;
    }
    else{
        exit("验证码输入错误");
    }
}