Created
April 29, 2014 15:12
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PHP Captcha
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<?php | |
/* | |
* File: CaptchaSecurityImages.php | |
* Author: Simon Jarvis | |
* Copyright: 2006 Simon Jarvis | |
* Date: 03/08/06 | |
* 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 | |
* | |
*/ | |
putenv('GDFONTPATH=' . realpath('.')); | |
session_start(); | |
class CaptchaSecurityImages { | |
private $font = 'monofont'; | |
public function __construct($width='120',$height='40',$characters='6') { | |
if( $characters < 3 ) { | |
die('Too few characters, insecure'); | |
} | |
$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, 255, 255, 255); | |
$text_color = imagecolorallocate($image, 20, 40, 100); | |
$noise_color = imagecolorallocate($image, 100, 120, 180); | |
/* 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); | |
$x = ($width - $textbox[4])/2; | |
$y = ($height - $textbox[5])/2; | |
imagettftext($image, $font_size, 0, $x, $y, $text_color, $this->font , $code); | |
/* output captcha image to browser */ | |
imagejpeg($image); | |
imagedestroy($image); | |
$_SESSION['security_code'] = $code; | |
} | |
private function generateCode($characters=6) { | |
/* list all possible characters, similar looking characters and vowels have been removed */ | |
$possible = '23456789bcdfghjkmnpqrstvwxyz'; | |
$i = 0; | |
while ($i < $characters) { | |
$code .= substr($possible, mt_rand(0, strlen($possible)-1), 1); | |
$i++; | |
} | |
return $code; | |
} | |
} | |
header('Content-Type: image/jpeg'); | |
$captcha = new CaptchaSecurityImages(); | |
?> |
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