Patch captcha

<?php

  /******************************************************************

   Projectname:   CAPTCHA class
   Version:       2.0
   Author:        Pascal Rehfeldt <Pascal@Pascal-Rehfeldt.com>
   Last modified: 15. January 2006

   * GNU General Public License (Version 2, June 1991)
   *
   * This program is free software; you can redistribute
   * it and/or modify it under the terms of the GNU
   * General Public License as published by the Free
   * Software Foundation; either version 2 of the License,
   * or (at your option) any later version.
   *
   * This program is distributed in the hope that it will
   * be useful, but WITHOUT ANY WARRANTY; without even the
   * implied warranty of MERCHANTABILITY or FITNESS FOR A
   * PARTICULAR PURPOSE. See the GNU General Public License
   * for more details.

   Description:
   This class can generate CAPTCHAs, see README for more details!

  ******************************************************************/

class captcha {

    private $_fontPath = 'Includes/font/';

    private $_fonts = array();

    private $_captchaString;

    public function create($captchaString) {
        if (function_exists('imagettftext') == false)
            trigger_error(__METHOD__ .'() : GD library don\'t exist !', E_USER_ERROR);

        $this->_fonts = $this->_getFonts();

        $this->_captchaString = $captchaString;

        $this->_makeCaptcha();
    }

    private function _getFonts() {
        if (! is_dir($this->_fontPath))
            trigger_error(__METHOD__ .'() : Font path don\'t exist ! ('. $this->_fontPath .')', E_USER_ERROR);

        $fonts = array();

        foreach (array_diff(scandir($this->_fontPath), array('.', '..')) as $file) {
            if (strtolower(pathinfo($this->_fontPath . $file, PATHINFO_EXTENSION )) == 'ttf')
                $fonts[] = $file;
        }

        if (count($fonts) == 0)
            trigger_error(__METHOD__ .'() : No font available for generate Captcha !', E_USER_ERROR);

        return $fonts;
    }

    public static function stringGen() {
        $charPool   = array_merge(range('A', 'Z'), range(0, 9));
        $poolLength = count($charPool) - 1;
        $str        = '';

        for ($i = 0; $i < CAPTCHA_LENGTH; $i++)
            $str .= $charPool[mt_rand(0, $poolLength)];

        return $str;
    }

    private function _getRandFont() {
        return $this->_fontPath . $this->_fonts[mt_rand(0, count($this->_fonts) - 1 )];
    }

    private function _makeCaptcha() {
        //header('Content-type: image/png');

        $imageLength = CAPTCHA_LENGTH * 25 + 16;
        $imageHeight = 50;

        $image       = imagecreate($imageLength, $imageHeight);
        $bgColor     = imagecolorallocate($image, 255, 255, 255);
        $stringColor = imagecolorallocate($image, 0, 0, 0);

        $filter = new captchaFilters($imageLength, $imageHeight);

        $filter->signs($image, $this->_getRandFont());

        $captchaStringLength = strlen((string) $this->_captchaString);

        for ($i = 0; $i < $captchaStringLength; $i++) {
            imagettftext(
                $image,
                20,
                mt_rand(-15, 15),
                $i * 25 + 10,
                mt_rand(25, 45),
                $stringColor,
                $this->_getRandFont(),
                $this->_captchaString{$i}
            );
        }

        $filter->noise($image, CAPTCHA_NOISE);
        $filter->blur($image, CAPTCHA_BLUR);

        imagepng($image);
        imagedestroy($image);
    }

}

?>