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<?php defined('SYSPATH') OR die('No direct access allowed.');
/**
* Captcha driver class.
*
* $Id: Captcha.php 3769 2008-12-15 00:48:56Z zombor $
*
* @package Captcha
* @author Kohana Team
* @copyright (c) 2007-2008 Kohana Team
* @license http://kohanaphp.com/license.html
*/
abstract class Captcha_Driver {
// The correct Captcha challenge answer
protected $response;
// Image resource identifier and type ("png", "gif" or "jpeg")
protected $image;
protected $image_type = 'png';
/**
* Constructs a new challenge.
*
* @return void
*/
public function __construct()
{
// Generate a new challenge
$this->response = $this->generate_challenge();
// Store the correct Captcha response in a session
Event::add('system.post_controller', array($this, 'update_response_session'));
}
/**
* Generate a new Captcha challenge.
*
* @return string the challenge answer
*/
abstract public function generate_challenge();
/**
* Output the Captcha challenge.
*
* @param boolean html output
* @return mixed the rendered Captcha (e.g. an image, riddle, etc.)
*/
abstract public function render($html);
/**
* Stores the response for the current Captcha challenge in a session so it is available
* on the next page load for Captcha::valid(). This method is called after controller
* execution (in the system.post_controller event) in order not to overwrite itself too soon.
*
* @return void
*/
public function update_response_session()
{
Session::instance()->set('captcha_response', sha1(strtoupper($this->response)));
}
/**
* Validates a Captcha response from a user.
*
* @param string captcha response
* @return boolean
*/
public function valid($response)
{
return (sha1(strtoupper($response)) === Session::instance()->get('captcha_response'));
}
/**
* Returns the image type.
*
* @param string filename
* @return string|FALSE image type ("png", "gif" or "jpeg")
*/
public function image_type($filename)
{
switch (strtolower(substr(strrchr($filename, '.'), 1)))
{
case 'png':
return 'png';
case 'gif':
return 'gif';
case 'jpg':
case 'jpeg':
// Return "jpeg" and not "jpg" because of the GD2 function names
return 'jpeg';
default:
return FALSE;
}
}
/**
* Creates an image resource with the dimensions specified in config.
* If a background image is supplied, the image dimensions are used.
*
* @throws Kohana_Exception if no GD2 support
* @param string path to the background image file
* @return void
*/
public function image_create($background = NULL)
{
// Check for GD2 support
if ( ! function_exists('imagegd2'))
throw new Kohana_Exception('captcha.requires_GD2');
// Create a new image (black)
$this->image = imagecreatetruecolor(Captcha::$config['width'], Captcha::$config['height']);
// Use a background image
if ( ! empty($background))
{
// Create the image using the right function for the filetype
$function = 'imagecreatefrom'.$this->image_type($background);
$this->background_image = $function($background);
// Resize the image if needed
if (imagesx($this->background_image) !== Captcha::$config['width']
OR imagesy($this->background_image) !== Captcha::$config['height'])
{
imagecopyresampled
(
$this->image, $this->background_image, 0, 0, 0, 0,
Captcha::$config['width'], Captcha::$config['height'],
imagesx($this->background_image), imagesy($this->background_image)
);
}
// Free up resources
imagedestroy($this->background_image);
}
}
/**
* Fills the background with a gradient.
*
* @param resource gd image color identifier for start color
* @param resource gd image color identifier for end color
* @param string direction: 'horizontal' or 'vertical', 'random' by default
* @return void
*/
public function image_gradient($color1, $color2, $direction = NULL)
{
$directions = array('horizontal', 'vertical');
// Pick a random direction if needed
if ( ! in_array($direction, $directions))
{
$direction = $directions[array_rand($directions)];
// Switch colors
if (mt_rand(0, 1) === 1)
{
$temp = $color1;
$color1 = $color2;
$color2 = $temp;
}
}
// Extract RGB values
$color1 = imagecolorsforindex($this->image, $color1);
$color2 = imagecolorsforindex($this->image, $color2);
// Preparations for the gradient loop
$steps = ($direction === 'horizontal') ? Captcha::$config['width'] : Captcha::$config['height'];
$r1 = ($color1['red'] - $color2['red']) / $steps;
$g1 = ($color1['green'] - $color2['green']) / $steps;
$b1 = ($color1['blue'] - $color2['blue']) / $steps;
if ($direction === 'horizontal')
{
$x1 =& $i;
$y1 = 0;
$x2 =& $i;
$y2 = Captcha::$config['height'];
}
else
{
$x1 = 0;
$y1 =& $i;
$x2 = Captcha::$config['width'];
$y2 =& $i;
}
// Execute the gradient loop
for ($i = 0; $i <= $steps; $i++)
{
$r2 = $color1['red'] - floor($i * $r1);
$g2 = $color1['green'] - floor($i * $g1);
$b2 = $color1['blue'] - floor($i * $b1);
$color = imagecolorallocate($this->image, $r2, $g2, $b2);
imageline($this->image, $x1, $y1, $x2, $y2, $color);
}
}
/**
* Returns the img html element or outputs the image to the browser.
*
* @param boolean html output
* @return mixed html string or void
*/
public function image_render($html)
{
// Output html element
if ($html)
return '<img alt="Captcha" src="'.url::site('captcha/'.Captcha::$config['group']).'" width="'.Captcha::$config['width'].'" height="'.Captcha::$config['height'].'" />';
// Send the correct HTTP header
header('Content-Type: image/'.$this->image_type);
// Pick the correct output function
$function = 'image'.$this->image_type;
$function($this->image);
// Free up resources
imagedestroy($this->image);
}
} // End Captcha Driver
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