<?
    session_start();
    class captcha
    {
        public $CAPTCHA_TYPE_CALC = 1;
        public $CAPTCHA_TYPE_CHARS = 2;

        //Einstellungen
        private $stringLength = 6;
        private $calcMaxValue = 10;
        private $characters = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
        //Einstellungen

        public function create($type){
            header("Content-Type: image/png");

            if($type == $this->CAPTCHA_TYPE_CALC){
                $img = ImageCreate(300, 100);
                $black = ImageColorAllocate($img, 0 , 0, 0);

                $positionX = 70;
                $digit = Array(rand(0, $this->calcMaxValue), rand(0, $this->calcMaxValue));

                for($i = 0; $i < count($digit); $i++){
                    $rotation = rand(0, 30);
                    $r = rand(0,255);
                    $g = rand(0,255);
                    $b = rand(0,255);
                    $white = ImageColorAllocate($img, $r, $b, $g);
                    imagettftext($img, 30.5, $rotation, $positionX, 60, $white, "./fonts/TAHOMA.TTF", $digit[$i]);
                    if($i == 0){
                        $positionX += 90;
                        imagettftext($img, 30.5, $rotation, $positionX, 60, $white, "./fonts/TAHOMA.TTF", "+");
                    }
                    $positionX += 90;
                }
                $_SESSION["calcResult"] = $digit[0] + $digit[1];
            }else if($type == $this->CAPTCHA_TYPE_CHARS){
                $img = ImageCreate($this->stringLength * 50, 100);
                $black = ImageColorAllocate($img, 0 , 0, 0);

                $positionX = 70;
                for($i = 0; $i < $this->stringLength; $i++) {
                    $rotation = rand(0, 45);
                    $r = rand(0,255);
                    $g = rand(0,255);
                    $b = rand(0,255);
                    $white = ImageColorAllocate($img, $r, $b, $g);
                    $char = $this->characters[rand(0, strlen($this->characters))];
                    $size = rand(30, 50);
                    imagettftext($img, $size, $rotation, $positionX, 60, $white, "./fonts/ARIAL.TTF", $char);
                    $positionX += ($size - 10);
                    $string .= $char;
                }
                $_SESSION["charsResult"] = $string;
            }

            ImagePNG($img);
            ImageDestroy($img);
        }

        public function checkCaptcha($type, $result){
            if($type == $this->CAPTCHA_TYPE_CALC){
                if($result == $_SESSION["calcResult"]){
                    return true;
                }else{
                    return false;
                }
            }else if($type == $this->CAPTCHA_TYPE_CHARS){
                if($result == $_SESSION["charsResult"]){
                    return true;
                }else{
                    return false;
                }
            }
        }
    }
?>