root/trunk/system/libraries/Captcha.php

<?php defined('SYSPATH') or die('No direct script access.');
/**
 * Captcha library.
 *
 * $Id$
 *
 * @package    Core
 * @author     Kohana Team
 * @copyright  (c) 2007-2008 Kohana Team
 * @license    http://kohanaphp.com/license.html
 */
class Captcha_Core {

    // Config
    protected $font_path        = '';
    protected $font_name        = '';
    protected $width            = 150;
    protected $height           = 50;
    protected $background_image = '';
    protected $style            = 'basic';
    protected $num_chars        = 4;

    // Class internal variables
    protected $image;
    protected $color_black;
    protected $color_white;
    protected $spacing;
    protected $captcha_code;
    protected $numerals = array('zero', 'one', 'two', 'three', 'four', 'five', 'six', 'seven', 'eight', 'nine');

    /**
     * Creates a new Captcha instance.
     *
     * @throws  Kohana_Exception
     * @param   array  configuration
     * @return  void
     */
    public function __construct($config = array())
    {
        static $check;

        // Check that a suitable GD2 library is available
        ($check === NULL) and $check = function_exists('imagegd2');

        if ($check === FALSE)
            throw new Kohana_Exception('captcha.requires_GD2');

        // Load configuration
        $config += Config::item('captcha', FALSE, FALSE);

        $this->initialize($config);

        // If using a background image, check if it exists.
        if ($this->background_image)
        {
            if ( ! file_exists($this->background_image))
                throw new Kohana_Exception('captcha.file_not_found', $this->background_image);
        }

        // If using a font, check if it exists.
        if ($this->font_name)
        {
            if ( ! file_exists($this->font_path.$this->font_name))
                throw new Kohana_Exception('captcha.file_not_found', $this->font_path.$this->font_name);
        }

        Log::add('debug', 'Captcha Library initialized');
    }

    /**
     * Sets or overwrites config values.
     *
     * @param   array  configuration
     * @return  void
     */
    public function initialize($config)
    {
        // Assign config values to the object
        foreach ($config as $key => $value)
        {
            if (property_exists($this, $key))
            {
                $this->$key = $value;
            }
        }
    }

    /**
     * Sets the Captcha code to use.
     *
     * @param   string  captcha code generated in captcha controller
     * @return  void
     */
    public function set_code($str)
    {
        $this->captcha_code = (string) $str;
    }

    /**
     * Generates the Captcha image.
     *
     * @return  void
     */
    public function render()
    {
        // If extending the class with a custom Captcha function, name it 'xyz_captcha'.
        // Style 'xyz' must be added to config. Now call the method that implements the Captcha.
        $this->{$this->style.'_captcha'}();

        // Tell browser what to expect
        // TODO: make this automatic
        // header('Content-Type: image/jpeg');
        header('Content-Type: image/png');

        // Output the captcha image
        // imagejpeg($this->image);
        imagepng($this->image);

        // Free up resources
        imagedestroy($this->image);
    }

    /**
     * Validates the Captcha code against session Captcha code
     *
     * @param   string   captcha code text
     * @return  boolean
     */
    public static function valid_captcha($str)
    {
        return (strtoupper($str) === strtoupper(Session::instance()->get('captcha_code')));
    }

    /**
     * Creates image resource and allocates some basic colors.
     * If a background image is supplied, the image dimensions are used.
     *
     * @return  void
     */
    protected function img_create()
    {
        if ($this->background_image)
        {
            // TODO: create from any valid image
            $this->image = imagecreatefromjpeg($this->background_image);
            $this->color_white = imagecolorallocate($this->image, 255, 255, 255);

            // Get the background image dimensions
            $this->width  = imagesx($this->image);
            $this->height = imagesy($this->image);
        }
        else
        {
            $this->image = imagecreatetruecolor($this->width, $this->height);
            $this->color_white = imagecolorallocate($this->image, 255, 255, 255);

            // Fill the image with a colored gradient (use random colors, but try not to obscure text)
            $left_color  = array(mt_rand(100,255), 0, 255);
            $right_color = array(100, 100, mt_rand(100,0));
            $this->img_color_gradient($this->image, 0, 0, $this->height, $this->width, $left_color, $right_color);
        }
    }

    /**
     * Allocates a background color to image.
     *
     * @param   array  GD image color identifier
     * @return  void
     */
    protected function img_background($color)
    {
        imagefill($this->image, 0, 0, $color);
    }

    /**
     * Draws a very basic Captcha image.
     * Requires only GD. Useful for testing or if you can't use truetype fonts.
     *
     * @return  void
     */
    protected function basic_captcha()
    {
        $this->image       = imagecreate($this->width, $this->height);
        $this->color_white = imagecolorallocate($this->image, 255, 255, 255);
        $this->color_black = imagecolorallocate($this->image, 0, 0, 0);

        imagestring($this->image, 5, 50, 15, $this->captcha_code, $this->color_black);
    }

    /**
     * Draws the standard Captcha image:
     * Requires GD with freetype and available truetype compatible font files.
     *
     * @param   none
     * @return  void
     */
    protected function standard_captcha()
    {
        $this->img_create();

        $font = $this->font_path.$this->font_name;
        $this->calculate_spacing();

        // Draw each Captcha character with varying attributes
        for ($i = 0, $strlen = strlen($this->captcha_code); $i < $strlen; $i++)
        {
            // Allocate random color, size and rotation attributes to text
            $text_color = imagecolorallocate($this->image, mt_rand(0, 100), mt_rand(0, 100), mt_rand(0, 100));
            $angle = mt_rand(-40, 40);

            // Make first char angle inward
            if ($i === 0)
            {
                $angle = -abs($angle);
            }
            // Make last char angle inward
            if ($i === ($this->num_chars - 1))
            {
                $angle = abs($angle);
            }

            // Scale the character size on image height
            $font_size = mt_rand($this->height - 20, $this->height - 12);
            $char_details = imageftbbox($font_size, $angle, $font, $this->captcha_code[$i], array());

            // Calculate character starting coordinates
            $iX = $this->spacing / 4 + $i * $this->spacing;
            $char_height = $char_details[2] - $char_details[5];
            $iY = $this->height / 2 + $char_height / 4;

            // Write text character to image
            imagefttext($this->image, $font_size, $angle, $iX, $iY, $text_color, $font, $this->captcha_code[$i], array());
        }
    }

    /**
     * Draws the alphasoup Captcha image:
     * Requires GD with freetype and available truetype compatible font files.
     *
     * @param   none
     * @return  void
     */
    protected function alphasoup_captcha()
    {
        $this->img_create();
        $font = $this->font_path.$this->font_name;
        $text_color = imagecolorallocate($this->image, mt_rand(0, 100), mt_rand(0, 100), mt_rand(0, 100));
        $color_limit = mt_rand(96, 160);
        $fill_color = imageColorAllocate($this->image, mt_rand($color_limit, 255), mt_rand($color_limit, 255), mt_rand($color_limit, 255));
        imageFilledRectangle($this->image, 0, 0, $this->width, $this->height, $fill_color);
        $font_width = imageFontWidth(10);
        $chars = 'ABCDEFGHIJKLMNO';

        for($loop = 0; $loop < 20; $loop++)
        {
            $text_color = imageColorAllocate($this->image, mt_rand($color_limit + 8, 255), mt_rand($color_limit + 8, 255), mt_rand($color_limit + 8, 255));
            $char = substr($chars, mt_rand(0, 15), 1);
            imageTTFtext($this->image, mt_rand(23, 27), mt_rand(160, 200), mt_rand(-10, $this->width + 10), mt_rand(-10, 60), $text_color, $font, $char);
        }

        $this->calculate_spacing();
        // Draw each Captcha character with varying attributes
        for ($i = 0, $strlen = strlen($this->captcha_code); $i < $strlen; $i++)
        {
            // Allocate random color, size and rotation attributes to text
            $text_color = imagecolorallocate($this->image, mt_rand(0, 100), mt_rand(0, 100), mt_rand(0, 100));
            $angle = mt_rand(-40, 40);

            // Make first char angle inward
            if ($i === 0)
            {
                $angle = -abs($angle);
            }
            // Make last char angle inward
            if ($i === ($this->num_chars - 1))
            {
                $angle = abs($angle);
            }

            // Scale the character size on image height
            $font_size = mt_rand($this->height - 20, $this->height - 12);
            $char_details = imageftbbox($font_size, $angle, $font, $this->captcha_code[$i], array());

            // Calculate character starting coordinates
            $iX = $this->spacing / 4 + $i * $this->spacing;
            $char_height = $char_details[2] - $char_details[5];
            $iY = $this->height / 2 + $char_height / 4;

            // Write text character to image
            imagefttext($this->image, $font_size, $angle, $iX, $iY, $text_color, $font, $this->captcha_code[$i], array());
        }

    }

    /**
     * Draws the math riddle Captcha image.
     * Requires GD with freetype and available truetype compatible font files.
     *
     * @return  void
     */
    protected function math_captcha()
    {
        $answer = Session::instance()->get('captcha_code');

        // Convert to numeral
        $numeral = $this->numerals[substr($answer, -1)];

        // Subtract last digit from answer
        $number = substr($answer, 0, 2).'0';

        // $number plus $numeral equals $answer
        $text = $number.' + '.$numeral.' = ';
        $this->img_create();
        $font = $this->font_path.$this->font_name;

        // Scale the font size to image height
        $font_size = $this->height / 3;
        $text_details = imageftbbox($font_size, 0, $font, $text, array());
        $iX = 5;
        $iY = ($this->height / 2) + 5;

        imagefttext($this->image, $font_size, 0, $iX, $iY, $this->color_white, $font, $text, array());
    }

    /**
     * Calculates letter spacing for truetype font characters.
     *
     * @return  integer
     */
    protected function calculate_spacing()
    {
        return $this->spacing = (int) $this->width / $this->num_chars;
    }

    /**
     * Fills the image with a colored gradient.
     *
     * @param   resource  gd image resource identifier
     * @param   integer   start X position
     * @param   integer   start Y position
     * @param   integer   height of fill in pixels
     * @param   integer   width of fill in pixels
     * @param   resource  gd image color identifier for left of image
     * @param   resource  gd image color identifier for right of image
     * @return  void
     */
    protected function img_color_gradient($image, $x1, $y1, $height, $width, $left_color, $right_color)
    {
        $color0 = ($left_color[0] - $right_color[0]) / $width;
        $color1 = ($left_color[1] - $right_color[1]) / $width;
        $color2 = ($left_color[2] - $right_color[2]) / $width;

        for ($i = 0; $i <= $width; $i++)
        {
            $red   = $left_color[0] - floor($i * $color0);
            $green = $left_color[1] - floor($i * $color1);
            $blue  = $left_color[2] - floor($i * $color2);
            $col   = imagecolorallocate($this->image, $red, $green, $blue);

            imageline($this->image, $x1 + $i, $y1, $x1 + $i, $y1 + $height, $col);
        }
    }

} // End Captcha Class