/core/captcha.php

<?php
/**
 * ???????
 * @copyright (c) Emlog All Rights Reserved
 * @version emlog-3.5.0
 * $Id: checkcode.php 1698 2010-05-03 03:57:40Z emloog@gmail.com $
 */
if(!defined('RQ_ROOT')) exit('Access Denied');

doAction('captcha_create_myself');

session_start();

$randCode = '';
$chars = 'abcdefghjkmnpqrstuvwxyzABCDEFGHJKLMNPRSTUVWXYZ23456789';
for ( $i = 0; $i < 4; $i++ ){
	$randCode .= substr($chars, mt_rand(0, strlen($chars) - 1), 1);
}

$_SESSION['code'] = strtoupper($randCode);

$img = imagecreate(55,22);
$bgColor = isset($_GET['mode']) && $_GET['mode'] == 't' ? imagecolorallocate($img,245,245,245) : imagecolorallocate($img,255,255,255);
$pixColor = imagecolorallocate($img,mt_rand(30, 180), mt_rand(10, 100), mt_rand(40, 250));

for($i = 0; $i < 4; $i++){
	$x = $i * 13 + mt_rand(0, 4) - 2;
	$y = mt_rand(0, 3);
	$text_color = imagecolorallocate($img, mt_rand(30, 180), mt_rand(10, 100), mt_rand(40, 250));
	imagechar($img, 5, $x + 5, $y + 3, $randCode[$i], $text_color);
}
for($j = 0; $j < 50; $j++){
	$x = mt_rand(0,55);
	$y = mt_rand(0,22);
	imagesetpixel($img,$x,$y,$pixColor);
}

header('Content-Type: image/png');
imagepng($img);
imagedestroy($img);
exit();