<?
/*
	This is PHP file that generates CAPTCHA image for the How to Create CAPTCHA Protection using PHP and AJAX Tutorial

	You may use this code in your own projects as long as this 
	copyright is left in place.  All code is provided AS-IS.
	This code 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.
	
	For the rest of the code visit http://www.WebCheatSheet.com
	
	Copyright 2006 WebCheatSheet.com	

*/

//Start the session so we can store what the security code actually is
session_start();

class CaptchaSecurityImages {

	var $font = 'monofont.ttf';

	function generateCode($characters) {
		/* list all possible characters, similar looking characters and vowels have been removed */
		$possible = '23456789bcdfghjkmnpqrstvwxyzABCDEFGHIJKLMNPQRSTUVWXYZ';
		$code = '';
		$i = 0;
		while ($i < $characters) { 
			$code .= substr($possible, mt_rand(0, strlen($possible)-1), 1);
			$i++;
		}
		return $code;
	}

	function CaptchaSecurityImages($width='60',$height='30',$characters='5') {
		$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) 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'] : '60';
$height = isset($_GET['height']) ? $_GET['height'] : '25';
$characters = isset($_GET['characters']) && $_GET['characters'] > 1 ? $_GET['characters'] : '5';

$captcha = new CaptchaSecurityImages($width,$height,$characters);
?>