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Derek Jones edited this page Jul 4, 2012 · 3 revisions

Simple Captcha is the modified version of Drupal's captcha module. This library will generate a simple captcha image with the specified noise and distortion ratios. The reason for using Drupal's code base for this captcha library is because of its variety of font support, distortion and noise settings in the generated captcha image. AJAX based refresh for new set of words makes the library more attractive.

The combination of flexible architecture of CodeIgniter & Drupal's expertise in GD libraries will make this module an essential ingredients for the registration pages.

Library file:

Place it inside /application/libraries/drupalcaptcha.php

<?php
/**
* Library for Image captcha
* Code Courtesy: Drupal Captcha Module
* @author Sastha L
*/

session_start();

define('IMAGE_CAPTCHA_ALLOWED_CHARACTERS', 'aAbBCdEeFfGHhijKLMmNPQRrSTtWXYZ23456789123456789@#$%&*');
//define('IMAGE_CAPTCHA_ALLOWED_CHARACTERS', 'abcdefghijklmnopqrstuvwxyz');
class drupalcaptcha
{
    /*
    * _Constructor
    */
    function drupalcaptcha()
    {
        //$this->createCaptcha();
    }
    /**
    * Function for initiate image creation process
    */
    function createCaptcha()
    {
        if(isset($_SESSION['captcha']['solution']))
            unset($_SESSION['captcha']['solution']);
        $seed    = $this->image_captcha_captcha();
        $this->image_captcha_image($seed['seed']);
    }
    /*
    * Function to find the seed value for image creation
    *
    */
    function image_captcha_captcha()
    {
        list($font, $errmsg) = $this->_image_captcha_get_font();
        $allowed_chars = $this->_image_captcha_utf8_split(IMAGE_CAPTCHA_ALLOWED_CHARACTERS);
        $code_length = 5;
        $code = '';
        for ($i = 0; $i < $code_length; $i++) {
          $code .= $allowed_chars[array_rand($allowed_chars)];
        }
        // store the answer in $_SESSION for the image generator function (which happens in another http request)
        $seed = mt_rand();
        $_SESSION['image_captcha'][$seed] = $code;

        $_SESSION['captcha']['solution'] = $code;   
        // build the result to return
        $result = array();
        $result['seed']     = $seed;
        $result['solution'] = $code;
        return $result;
    }
    /**
    * Main image creation function
    * 
    */
    function image_captcha_image($seed=NULL) 
    {
        if(!$seed)
        {
            echo 'exit';
            return;
        }
        // get the code to draw from $_SESSION
        $code = $_SESSION['image_captcha'][$seed];
        // unset the code from $_SESSION to prevent rerendering the CAPTCHA
        unset($_SESSION['image_captcha'][$seed]);
        // only generate an image if there is an code
        if ($code) {
            // generate the image
            $image = $this->_image_captcha_generate_image($code);
            // check of generation was successful
            if (!$image) {
              echo 'Generation of image CAPTCHA failed. Check your image CAPTCHA configuration and especially the used font.';
              exit();
            }
            //return $image;
            // Send the image resource as an image to the client
            header("Content-type: image/jpeg");
            // Following header is needed for Konqueror, which would re-request the image
            // on a mouseover event, which failes because the image can only be generated
            // once. This cache directive forces Konqueror to use cache instead of
            // re-requesting
            //header("Cache-Control: max-age=3600, must-revalidate");
            // print the image as jpg to the client
            imagejpeg($image);
            // Clean up
            imagedestroy($image);
            exit();
        }
    }
    /**
 * base function for generating a image CAPTCHA
 */
function _image_captcha_generate_image($code) {

    // get font
    list($font, $errmsg) = $this->_image_captcha_get_font();
    if (!$font) 
    {
        echo 'Font is not available';
        exit();
    }
    // get other settings
    $font_size = 30;
    $character_spacing = '1.2';
    $characters = $this->_image_captcha_utf8_split($code);
    $character_quantity = count($characters);
    $width = 163; //$character_spacing * $font_size * $character_quantity;
    $height = 2 * $font_size;

    // create image resource
    $image = imagecreatetruecolor($width, $height);
    if (!$image) 
    {
        return FALSE;
    }

    // background
    $background_color = imagecolorallocate($image, 255, 255, 255);
    imagefilledrectangle($image, 0, 0, $width, $height, $background_color);
    $doubleVision = false;
    // draw text
    //if (variable_get('image_captcha_double_vision', 0)) {
    if ($doubleVision) {
        $result = $this->_image_captcha_image_generator_print_string($image, $width, $height, $font, $font_size, $code, TRUE);
        if (!$result) 
        {
          return FALSE;
        }
    }
    $result = $this->_image_captcha_image_generator_print_string($image, $width, $height, $font, $font_size, $code, FALSE);
    if (!$result) 
    {
        return FALSE;
    }

    // add noise
    $noise_colors = array();
    for ($i = 0; $i < 20; $i++) {
        $noise_colors[] = imagecolorallocate($image, mt_rand(0, 255), mt_rand(0, 255), mt_rand(0, 255));
    }
      
    // Add additional noise.
    $dotNoise    = 1;
    //if (variable_get('image_captcha_dot_noise', 0)) {
    if ($dotNoise) {
        $this->_image_captcha_image_generator_add_dots($image, $width, $height, $noise_colors);
      }
      $lineNoise    = 0;
      //if (variable_get('image_captcha_line_noise', 0)) {
      if ($lineNoise) {
        $this->_image_captcha_image_generator_add_lines($image, $width, $height, $noise_colors);
      }

      // Distort the image.
      $distortion_amplitude = .25 * $font_size * 1 / 10.0;
      if ($distortion_amplitude > 1) 
      {
        // distortion parameters
        $wavelength_xr = (2+3*lcg_value())*$font_size;
        $wavelength_yr = (2+3*lcg_value())*$font_size;
        $freq_xr = 2 * 3.141592 / $wavelength_xr;
        $freq_yr = 2 * 3.141592 / $wavelength_yr;
        $wavelength_xt = (2+3*lcg_value())*$font_size;
        $wavelength_yt = (2+3*lcg_value())*$font_size;
        $freq_xt = 2 * 3.141592 / $wavelength_xt;
        $freq_yt = 2 * 3.141592 / $wavelength_yt;

        $distorted_image = imagecreatetruecolor($width, $height);
        if (!$distorted_image) {
          return FALSE;
        }
        $bilinairInterpolation    = true;
       //if (variable_get('image_captcha_bilinair_interpolation', FALSE)) {
       if ($bilinairInterpolation) {
            // distortion with bilineair interpolation
            for ($x = 0; $x < $width; $x++) {
                for ($y = 0; $y < $height; $y++) {
                    // get distorted sample point in source image
                    $r = $distortion_amplitude * sin($x * $freq_xr + $y * $freq_yr);
                    $theta = $x * $freq_xt + $y * $freq_yt;
                    $sx = $x + $r * cos($theta);
                    $sy = $y + $r * sin($theta);
                    $sxf = (int)floor($sx);
                    $syf = (int)floor($sy);
                    if ($sxf < 0 || $syf < 0 || $sxf >= $width - 1 || $syf >= $height - 1) {
                        $color = $background_color;
                    }else {
                        // bilineair interpolation: sample at four corners
                        $color_00 = imagecolorat($image, $sxf  , $syf  );
                        $color_00_r = ($color_00 >> 16) & 0xFF;
                        $color_00_g = ($color_00 >> 8) & 0xFF;
                        $color_00_b = $color_00 & 0xFF;
                        $color_10 = imagecolorat($image, $sxf+1, $syf  );
                        $color_10_r = ($color_10 >> 16) & 0xFF;
                        $color_10_g = ($color_10 >> 8) & 0xFF;
                        $color_10_b = $color_10 & 0xFF;
                        $color_01 = imagecolorat($image, $sxf  , $syf+1);
                        $color_01_r = ($color_01 >> 16) & 0xFF;
                        $color_01_g = ($color_01 >> 8) & 0xFF;
                        $color_01_b = $color_01 & 0xFF;
                        $color_11 = imagecolorat($image, $sxf+1, $syf+1);
                        $color_11_r = ($color_11 >> 16) & 0xFF;
                        $color_11_g = ($color_11 >> 8) & 0xFF;
                        $color_11_b = $color_11 & 0xFF;
                        // interpolation factors
                        $u  = $sx - $sxf;
                        $v  = $sy - $syf;
                        // interpolate
                        $r = (int)((1-$v)*((1-$u)*$color_00_r + $u*$color_10_r) + $v*((1-$u)*$color_01_r + $u*$color_11_r));
                        $g = (int)((1-$v)*((1-$u)*$color_00_g + $u*$color_10_g) + $v*((1-$u)*$color_01_g + $u*$color_11_g));
                        $b = (int)((1-$v)*((1-$u)*$color_00_b + $u*$color_10_b) + $v*((1-$u)*$color_01_b + $u*$color_11_b));
                        // build color
                        $color = ($r<<16) + ($g<<8) + $b;
                    }
                    imagesetpixel($distorted_image, $x, $y, $color);
                }
            }
        }else {
            // distortion with nearest neighbor interpolation
            for ($x = 0; $x < $width; $x++) {
                for ($y = 0; $y < $height; $y++) {
                    // get distorted sample point in source image
                    $r = $distortion_amplitude * sin($x * $freq_xr + $y * $freq_yr);
                    $theta = $x * $freq_xt + $y * $freq_yt;
                    $sx = $x + $r * cos($theta);
                    $sy = $y + $r * sin($theta);
                    $sxf = (int)floor($sx);
                    $syf = (int)floor($sy);
                    if ($sxf < 0 || $syf < 0 || $sxf >= $width - 1 || $syf >= $height - 1) {
                        $color = $background_color;
                    }else {
                        $color = imagecolorat($image, $sxf, $syf);
                    }
                    imagesetpixel($distorted_image, $x, $y, $color);
                }
            }
        }
        // release undistorted image
        imagedestroy($image);
        //echo 'asdf';print_r($image);exit;
        // return distorted image
        return $distorted_image;
        }else{
            return $image;
        }
}
/**
 * Returns:
 *  - the path to the image CAPTCHA font or FALSE when an error occured
 *  - error message
*/
function _image_captcha_get_font() {
    $font = 'fonts/times.ttf';
    //$font    = realpath(dirname(__FILE__)).'/fonts/arial.ttf';
    $errmsg = FALSE;
    if ($font != 'BUILTIN' && (!is_file&#40;$font&#41; || !is_readable($font))) {
        echo $errmsg = 'Could not find or read the configured font "'.$font.'" for the image captcha.';
        $font = FALSE;
    }
    return array($font, $errmsg);
}
/**
 * Helper function for splitting an utf8 string correctly in characters.
 * Assumes the given utf8 string is well formed.
 * See http://en.wikipedia.org/wiki/Utf8 for more info
 */
function _image_captcha_utf8_split($str) {
    $characters = array();
    $len = strlen($str);
    for ($i=0; $i < $len; ) 
    {
        $chr = ord($str[$i]);
        if (($chr & 0x80) == 0x00) { // one byte character (0zzzzzzz)
            $width = 1;
        }else {
            if (($chr & 0xE0) == 0xC0) { // two byte character (first byte: 110yyyyy)
                $width = 2;
            }
            elseif (($chr & 0xF0) == 0xE0) { // three byte character (first byte: 1110xxxx)
                $width = 3;
            }
            elseif (($chr & 0xF8) == 0xF0) { // four byte character (first byte: 11110www)
                $width = 4;
            }
            else {
                echo 'Encountered an illegal byte while splitting an utf8 string in characters.';
                return $characters;
            }
        }
        $characters[] = substr($str, $i, $width);
        $i += $width;
    }
    return $characters;
}
/**
* Function to print the seed over image
*/
function _image_captcha_image_generator_print_string(&$image, $width, $height, $font, $font_size, $text, $light_colors=FALSE) {
    // get characters
    $characters = $this->_image_captcha_utf8_split($text);
    $character_quantity = count($characters);
    // get total width
    if ($font == 'BUILTIN') {
        $character_width = imagefontwidth(5);
        $character_height = imagefontheight(5);
        $textwidth = $character_quantity * $character_width;
    }
    else {
        $bbox = imagettfbbox($font_size, 0, realpath($font), $text);
        if (!$bbox) {
        return FALSE;
        }
        $textwidth = $bbox[2] - $bbox[0];
    }
    // calculate spacing
    $spacing = ($width - $textwidth) / ($character_quantity + 1);
    // character jittering
    $jittering_x = .3 * $font_size;
    $jittering_y = .3 * $font_size;
    // start cursor
    $x = $spacing;
    foreach ($characters as $character) {
        // get character dimensions
        if ($font != 'BUILTIN') {
          $bbox = imagettfbbox($font_size, 0, realpath($font), $character);
          $character_width = $bbox[2] - $bbox[0];
          $character_height = $bbox[5] - $bbox[3];
        }
        // calculate y position
        $y = .5 * ($height - $character_height);
        // generate random color
        if ($light_colors) {
          $color = imagecolorallocate($image, mt_rand(128, 255), mt_rand(128, 255), mt_rand(128, 255));
        }
        else {
          $color = imagecolorallocate($image, mt_rand(0, 127), mt_rand(0, 127), mt_rand(0, 127));
        }
        // add jitter to position
        $pos_x = $x + mt_rand(-$jittering_x, $jittering_x);
        $pos_y = $y + mt_rand(-$jittering_y, $jittering_y);
        // draw character
        if ($font == 'BUILTIN') {
          imagestring($image, 5, $pos_x, $pos_y, $character, $color);
        } else {
          imagettftext($image, $font_size, 0, $pos_x, $pos_y, $color, realpath($font), $character);
        }
        // shift cursor
        $x += $character_width + $spacing;
    }
    // return a sign of success
    return TRUE;
}    
/**
* Function place lines in the image background
*/
function _image_captcha_image_generator_add_lines(&$image, $width, $height, $colors) {
    $line_quantity = $width * $height/200.0 * (5) / 10.0;
    for ($i = 0; $i <  $line_quantity; $i++) 
    {
        imageline($image, mt_rand(0, $width), mt_rand(0, $height), mt_rand(0, $width), mt_rand(0, $height), $colors[array_rand($colors)]);
    }
}
/**
* Function place dots in the image background
*/
function _image_captcha_image_generator_add_dots(&$image, $width, $height, $colors) {
    $noise_quantity = ($width * $height)/2.0 * (1) / 10.0;
    for ($i = 0; $i < $noise_quantity; $i++ ) 
    {
        imagesetpixel($image, mt_rand(0, $width), mt_rand(0, $height), $colors[array_rand($colors)]);
    }
}
/**
* Create a new image
*/
function get_captcha_image($seedInput = '')
{
    if($seedInput == "")
        exit;
    else
    {
        /*
        $seed = $seedInput;
        // get the code to draw from $_SESSION
        $code = $_SESSION['image_captcha'][$seed];
        // unset the code from $_SESSION to prevent rerendering the CAPTCHA
        unset($_SESSION['image_captcha'][$seed]);
        // only generate an image if there is an code
        if ($code) 
        {
            // generate the image
            $image = $this->_image_captcha_generate_image($code);
            // check of generation was successful
            if (!$image) {
                echo 'Generation of image CAPTCHA failed. Check your image CAPTCHA configuration and especially the used font.';
                exit();
            }
            // Send the image resource as an image to the client
            header("Content-type: image/jpeg");
            // Following header is needed for Konqueror, which would re-request the image
            // on a mouseover event, which failes because the image can only be generated
            // once. This cache directive forces Konqueror to use cache instead of
            // re-requesting
            header("Cache-Control: max-age=3600, must-revalidate");
            // print the image as jpg to the client
            imagejpeg($image);
            // Clean up
            imagedestroy($image);
            exit();
        }
        */
        $this->createCaptcha();
    }
    exit;
}
/*
set new Image
*/
function set_captcha_image()
{
    // generate a CAPTCHA code
    $allowed_chars = $this->_image_captcha_utf8_split(IMAGE_CAPTCHA_ALLOWED_CHARACTERS);
    $code_length = 5;
    $code = '';
    for ($i = 0; $i < $code_length; $i++) {
      $code .= $allowed_chars[array_rand($allowed_chars)];
    }
    $seed = mt_rand();
    $_SESSION['image_captcha'][$seed] = $code;
    $captcha_token=md5(mt_rand());
    $_SESSION['captcha']['solution']=$code;
    print $seed."^".$captcha_token;
    exit;
}
}
?&gt;

Controller file:

Place it inside /application/controllers/captcha.php

&lt;?php
/**
* Controller Class which is used for Captcha Image display in user registration
*
* @verison 1.0
* @author Sastha L
*/
class Captcha extends Controller {
    
    /**
    * _constructor Controller
    */
    function Captcha() 
    {
        parent::Controller();
        $this->load->library('drupalcaptcha');
        $this->captcha    = new drupalcaptcha();
    }
    /**
    *    Index Controller
    */
    function index() 
    {
        $this->captcha->createCaptcha();
    }
    /*
    * Function to display Captcha image on page load
    */
    function createNewImage()
    {
        $this->captcha->set_captcha_image();
    }
    /*
    * Function to display the src during AJAX call
    */
    function displayCaptcha($seed = '')
    {
        $this->captcha->get_captcha_image($seed);
    }
}
/* End of file captcha.php */
/* Location: ./system/application/controllers/captcha.php */
?&gt;

View File:

Place it inside /application/views/captcha.php

&lt;html&gt;
&lt;head&gt;
[removed]config->site_url();?&gt;js/jquery.js">[removed]
[removed]
var captcha_flag=false;

function ch_captcha(type,seed)
{


 var url='';
     url='&lt;?php echo $this->config->site_url();?&gt;';
var token='';

if(captcha_flag==true)
    return;

captcha_flag=true;


  var urls='';

      if(type==2 && seed==null)
      {
          //token_1=$("#edit-captcha-token").val();
          urls=url+"captcha/createNewImage";
      }
      else
          urls=url+"captcha/displayCaptcha/"+seed;


  $.ajax({
   type: "GET",
   url: urls,
   success: function(msg){

    captcha_flag=false;

    if(msg!="")
    {
        if(type==2 && seed==null)
        {
            var temp=msg;
            var pos=temp.indexOf("^");
            if(pos>1)
            {
                var arr=Array();
                arr=temp.split("^");
                seed=arr[0];
                token=arr[1];
                $("#img_cap").attr("src",""+url+"captcha/displayCaptcha/"+seed);
                $("#edit-captcha-token").val(token);
            }
            
            //ch_captcha(1,seed);
        }
    
    }
   },
   error: function(msg){

        captcha_flag=false;
   }
 });
}
[removed]
&lt;/head&gt;
&lt;/body&gt;
<table width="686" height="115" border="0" align="center" cellpadding="0" cellspacing="0">
 <tr>
      <td valign="top" align="right"></td>
      <td colspan="3">
        &lt;input type="hidden" name="captcha_token" value="&lt;?php echo md5(mt_rand()); ?&gt;" /&gt;
        <img >config->site_url('captcha')?&gt;" id="img_cap" alt="no-image"/><br />
        <a>Show new characters</a>
        <div class="bottomspacer"></div>        </td>
    </tr>

<tr>
    <td valign="top" align="right">Security Verification</td>
    <td width="150" valign="top">
    &lt;?php
    if(isset($captchaResponse))
    {
        $captchaResponse = $captchaResponse;
    }else{
        $captchaResponse = '';
    }
    ?&gt;
    &lt;input type="text" value="&lt;?=$captchaResponse?&gt;" size="25" id="edit-captcha-response" name="captcha_response" maxlength="5"/&gt;&lt;/td>
    <td width="156"><span class="helpcontent">Type the characters you see in the picture above. Letters are not case-sensitive
    </span></td>
    </tr>
</table>
&lt;/body&gt;
&lt;/html&gt;

This will generate a simple captcha image.

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