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<?php

/*

 *

 * this code is based on captcha code by Simon Jarvis 

 * 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

 *

 * 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

 */



session_start();

//Settings: You can customize the captcha here

$image_width = 120;

$image_height = 40;

$characters_on_image = 6;

$font = './monofont.ttf';



//The characters that can be used in the CAPTCHA code.
//avoid confusing characters (l 1 and i for example)

$possible_letters = '23456789bcdfghjkmnpqrstvwxyz';

$random_dots = 0;

$random_lines = 20;

$captcha_text_color = "0x142864";

$captcha_noice_color = "0x142864";



$code = '';





$i = 0;

while ($i < $characters_on_image) {

    $code .= substr($possible_letters, mt_rand(0, strlen($possible_letters) - 1), 1);

    $i++;
}





$font_size = $image_height * 0.75;

$image = @imagecreate($image_width, $image_height);





/* setting the background, text and noise colours here */

$background_color = imagecolorallocate($image, 255, 255, 255);



$arr_text_color = hexrgb($captcha_text_color);

$text_color = imagecolorallocate($image, $arr_text_color['red'], $arr_text_color['green'], $arr_text_color['blue']);



$arr_noice_color = hexrgb($captcha_noice_color);

$image_noise_color = imagecolorallocate($image, $arr_noice_color['red'], $arr_noice_color['green'], $arr_noice_color['blue']);





/* generating the dots randomly in background */

for ($i = 0; $i < $random_dots; $i++) {

    imagefilledellipse($image, mt_rand(0, $image_width), mt_rand(0, $image_height), 2, 3, $image_noise_color);
}





/* generating lines randomly in background of image */

for ($i = 0; $i < $random_lines; $i++) {

    imageline($image, mt_rand(0, $image_width), mt_rand(0, $image_height), mt_rand(0, $image_width), mt_rand(0, $image_height), $image_noise_color);
}





/* create a text box and add 6 letters code in it */

$textbox = imagettfbbox($font_size, 0, $font, $code);

$x = ($image_width - $textbox[4]) / 2;

$y = ($image_height - $textbox[5]) / 2;

imagettftext($image, $font_size, 0, $x, $y, $text_color, $font, $code);





/* Show captcha image in the page html page */

header('Content-Type: image/jpeg'); // defining the image type to be shown in browser widow

imagejpeg($image); //showing the image

imagedestroy($image); //destroying the image instance

$_SESSION['CAPTCHACODE'] = $code;

function hexrgb($hexstr) {

    $int = hexdec($hexstr);



    return array("red" => 0xFF & ($int >> 0x10),
        "green" => 0xFF & ($int >> 0x8),
        "blue" => 0xFF & $int);
}

?>