/libs/captcha/CaptchaSecurityImages.php

<?php
/*
 *  Copyright (C) 2010-2011  TrinityScripts <http://www.trinityscripts.xe.cx/>
 *
 *  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.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */
 
session_start();

/*
* File: CaptchaSecurityImages.php
* Author: Simon Jarvis
* Copyright: 2006 Simon Jarvis
* Date: 03/08/06
* Updated: 07/02/07
* Requirements: PHP 4/5 with GD and FreeType libraries
* Link: http://www.white-hat-web-design.co.uk/articles/php-captcha.php
*
* 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:
* http://www.gnu.org/licenses/gpl.html
*/

class CaptchaSecurityImages
{
    var $font = 'monofont.ttf';

    function generateCode($characters)
    {
        /* list all possible characters, similar looking characters and vowels have been removed */
        $possible = '23456789bcdfghjkmnpqrstvwxyz';
        $code = '';

        for($i=0; $i<$characters; ++$i)
            $code .= substr($possible, mt_rand(0, strlen($possible)-1), 1);
            
        return $code;
    }

    function CaptchaSecurityImages($width='350', $height='130', $characters='6')
    {
        $code = $this->generateCode($characters);
        /* font size will be 75% of the image height */
        $font_size = $height * 0.75;
        $image = @imagecreate($width, $height) or die('Cannot initialize new GD image stream');
        /* set the colours */
        $background_color = imagecolorallocate($image, 20, 20, 20);
        $text_color  = imagecolorallocate($image, 215, 235, 255);
        $noise_color = imagecolorallocate($image, 155, 175, 195);
        /* generate random dots in background */
        for($i=0; $i<($width*$height)/3; ++$i)
          imagefilledellipse($image, mt_rand(0,$width), mt_rand(0,$height), 1, 1, $noise_color);

        /* generate random lines in background */
        for($i=0; $i<($width*$height)/150; ++$i)
          imageline($image, mt_rand(0,$width), mt_rand(0,$height), mt_rand(0,$width), mt_rand(0,$height), $noise_color);

        /* create textbox and add text */
        $textbox = imagettfbbox($font_size, 0, $this->font, $code) or die('Error in imagettfbbox function');
        $x = ($width  - $textbox[4])/2;
        $y = ($height - $textbox[5])/2;
        imagettftext($image, $font_size, 0, $x, $y, $text_color, $this->font , $code) or die('Error in imagettftext function');
        /* output captcha image to browser */
        header('Content-Type: image/jpeg');
        imagejpeg($image);
        imagedestroy($image);
        $_SESSION['security_code'] = $code;
    }
}

$width      = isset($_GET['width']) ? $_GET['width'] : '350';
$height     = isset($_GET['height']) ? $_GET['height'] : '130';
$characters = isset($_GET['characters']) && 1 < $_GET['characters'] ? $_GET['characters'] : '8';

$captcha = new CaptchaSecurityImages($width, $height, $characters);


?>