PHP生成图片验证码

/** * 验证码类，用于产生各种验证码 */class captcha{    /**     * 生成验证码     * @param int $length 码字符长度     * @param int $width 宽度     * @param int $height 长度     * @param string $type 类型     * @return      */    public static function getCode($length=4,$width=50,$height=22,$type='png')     {        //session_start();        $randval = self::randString($length);        //$_SESSION['captcha']= $randval;                $width = ($length*9+10)>$width?$length*9+10:$width;        if ( $type!='gif' && function_exists('imagecreatetruecolor')) {            $im = @imagecreatetruecolor($width,$height);        }else {            $im = @imagecreate($width,$height);        }        $r = Array(225,255,255,223);        $g = Array(225,236,237,255);        $b = Array(225,236,166,125);        $key = mt_rand(0,3);        $backColor = imagecolorallocate($im, $r[$key],$g[$key],$b[$key]);    //背景色（随机）        $borderColor = imagecolorallocate($im, 100, 100, 100);                    //边框色        $pointColor = imagecolorallocate($im,mt_rand(0,255),mt_rand(0,255),mt_rand(0,255));            //点颜色        @imagefilledrectangle($im, 0, 0, $width - 1, $height - 1, $backColor);        @imagerectangle($im, 0, 0, $width-1, $height-1, $borderColor);        $stringColor = imagecolorallocate($im,mt_rand(0,200),mt_rand(0,120),mt_rand(0,120));        // 干扰        for($i=0;$i<10;$i++){            $fontcolor=imagecolorallocate($im,mt_rand(0,255),mt_rand(0,255),mt_rand(0,255));            imagearc($im,mt_rand(-10,$width),mt_rand(-10,$height),mt_rand(30,300),mt_rand(20,200),55,44,$fontcolor);        }        for($i=0;$i<25;$i++){            $fontcolor=imagecolorallocate($im,mt_rand(0,255),mt_rand(0,255),mt_rand(0,255));            imagesetpixel($im,mt_rand(0,$width),mt_rand(0,$height),$pointColor);        }        @imagestring($im, 10, 20, 10, $randval, $stringColor);           header("Content-type: Image/".$type);        $ImageFun='Image'.$type;        $ImageFun($im);        imagedestroy($im);         return $randval;    }}

 include "../lib/captcha.class.php"; $captcha = new captcha(); $checkCode = $captcha->getCode(4,75,32); echo $checkCode;