php Captcha 練習

突然有個想法，就是去寫一個簡單的驗證碼類，其實驗證碼在很多框架有自帶的，網上一搜也一大把，我只是想當作是練習，熟悉一下過程。

session_start();
class He_Captcha{
    
    private $str = "23456789abcdefghijkmnpqrstuvwxyzABCDEFGHIJKLMNPQRSTUVW";
    private $text;
    private $im;
    public    $num;
    public    $size;
    public    $width;
    public    $height;
    public    $session_var;
    public    $ttfs = array(
        'Jura.ttf',
        'AntykwaBold.ttf',
        'Duality.ttf',
        'VeraSansBold.ttf'
    );
    
    /*       生成驗證碼
     *num     顯示的驗證碼字符數
     *size    字符的字體大小
     *session_var   驗證碼會話名稱
     *width   驗證碼圖片的寬
     *height  驗證碼圖片的高
    */
    public function Captcha($num = 4, $size = 15, $session_var = '', $width = 0, $height = 0){

        $this->num = (int)max($this->num, $num);
        $this->size = (int)max($this->size, $size);
        $this->width = $width ? (int)max($this->width, $width) : $this->num * $this->size;
        $this->height = $height ? (int)max($this->height, $height) : $this->size + 10;
        $this->session_var = strlen(trim($session_var))>2 ? trim($session_var):'captcha';
        
        
        $this->_getText($this->num);
        $_SESSION[$this->session_var] = $this->text;
        $this->im = imagecreatetruecolor($this->width, $this->height);//畫圖像
         $this->_drowBackground();//畫背景
         $this->_setNoiseLines();//畫干擾線
         $this->_setNoisePoints();//畫干擾點
         $this->_writeText();//畫驗證碼
         $this->_createCaptcha();
    }
    
    /*創建驗證碼內容*/
    private function _getText($num){
        for( $i = 0; $i < $num; $i++ ){
            $this->text .= $this->str[mt_rand(0,strlen($this->str)-1)];
        }
    }
    
    /*畫背景*/
    private function _drowBackground(){
        $bg_color = imagecolorallocate($this->im, 235, 236, 237);
        imagefilledrectangle($this->im, 0, 0, $this->width, $this->height, $bg_color);
    }
    
    /*畫干擾點*/
    private function _setNoisePoints(){
        $points = 2 * $this->width;
        for($i = 0;$i < $points;$i++){
            $font_color = imagecolorallocate($this->im, mt_rand(0, 255), mt_rand(0, 255), mt_rand(0, 255));
            imagesetpixel($this->im, mt_rand(0, $this->width), mt_rand(0, $this->height), $font_color);
        }
    }
    /*畫干擾線*/
    private function _setNoiseLines(){
        $lines = $this->width / 12;
        for($i = 0; $i < $lines; $i++){
            $font_color = imagecolorallocate($this->im, mt_rand(0, 255), mt_rand(0, 255), mt_rand(0, 255));
            imagearc($this->im, mt_rand( -$this->width, $this->width), mt_rand( -$this->height, $this->height), mt_rand(30, $this->width * 2), mt_rand(20, $this->height * 2), mt_rand(0, 360), mt_rand(0, 360), $font_color);    
        }
    }
    /*畫驗證碼*/
    private function _writeText(){
        for($i = 0; $i < $this->num; $i++){
            $ttf = 'fonts/'.$this->ttfs[array_rand($this->ttfs,1)];
            $text_color = imagecolorallocate($this->im, mt_rand(0, 200), mt_rand(0, 120), mt_rand(0, 120));
            @imagefttext($this->im, $this->size, mt_rand(-10,10), $this->size*$i, $this->size+5, $text_color, $ttf, $this->text[$i]);
        }
    }
    
    /*生成驗證碼*/
    private function _createCaptcha(){
        header("Cache-Control: max-age=1, s-maxage=1, no-cache, must-revalidate");
        header("Content-Type: image/png; charset=utf-8");
        imagepng($this->im);
        imagedestroy($this->im);
    }
}

下面為調用以及生成效果：

$c = new He_Captcha();
$c->Captcha();

.........