/system/application/helpers/captcha_helper.php

<?php if (!defined('BASEPATH')) exit('No direct script access allowed');
/**
 * XtraUpload
 *
 * A turn-key open source web 2.0 PHP file uploading package requiring PHP v5
 *
 * @package		XtraUpload
 * @author		Matthew Glinski
 * @copyright	Copyright (c) 2006, XtraFile.com
 * @license		http://xtrafile.com/docs/license
 * @link		http://xtrafile.com
 * @since		Version 2.0
 * @filesource
 */

// ------------------------------------------------------------------------

/**
 * XtraUpload Captcha Image Helper
 *
 * @package		XtraUpload
 * @subpackage	Helper
 * @category	Helper
 * @author		Matthew Glinski
 * @link		http://xtrafile.com/docs/pages/files
 */

// ------------------------------------------------------------------------

function create_captcha($aCfg)
{
    // check, whether we do have a config-array given
    if(!is_array($aCfg))
    {
        // no config given!
        return FALSE;
    }    
    
    if (( !isset($aCfg['img_path']) or $aCfg['img_path'] == '') or (!isset($aCfg['img_url']) or $aCfg['img_url'] == ''))
	{
		return FALSE;
	}

	if ( ! @is_dir($aCfg['img_path']))
	{
		return FALSE;
	}
	
	if ( ! is_writable($aCfg['img_path']))
	{
		return FALSE;
	}
			
	if ( ! extension_loaded('gd'))
	{
		return FALSE;
	}		
	
	// the length of the word
    if ( !isset($aCfg['length']) or $aCfg['length'] == '')
	    $aCfg['length'] = 5;
	
	// Do we have a "word" yet?
    if ( !isset($aCfg['word']) or $aCfg['word'] == '')
    {
    	$pool = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';
    	$str = '';
    	for ($i = 0; $i < $aCfg['length']; $i++)
    	{
    		$str .= substr($pool, mt_rand(0, strlen($pool) -1), 1);
    	}
    	$aCfg['word'] = $str;
    }
    
    // where to find the fonts
    if( !isset($aCfg['font_path']) or $aCfg['font_path'] == '')
        $aCfg['font_path'] = BASEPATH.'fonts/';
    
    // what fonts to use in captcha image
    if( !isset($aCfg['fonts']) or !is_array($aCfg['fonts']) or $aCfg['fonts'] == '')
        $aCfg['fonts'] = array('texb.ttf');

    // fontsize in PT
    if( !isset($aCfg['font_size']) or $aCfg['font_size'] == '')    
        $aCfg['font_size'] = 18;  
    
    // width if the image in PX
    if( !isset($aCfg['img_width']) or $aCfg['img_width'] == '')
        $aCfg['img_width'] = 170; 
    
    // height of the image in PX
    if( !isset($aCfg['img_heigtht']) or $aCfg['img_height'] == '')
        $aCfg['img_height'] = 30;

    if(!isset($aCfg['expiration']) or $aCfg['expiration'] == '')
        $aCfg['expiration'] = 7200;

    // Set the enviroment variable for GD
    putenv('GDFONTPATH='.realpath('.')); 
    
    
	// Remove old images	
	list($usec, $sec) = explode(" ", microtime());
	$now = ((float)$usec + (float)$sec);
	$current_dir = opendir($aCfg['img_path']);
	while($filename = readdir($current_dir))
	{
		if ($filename != "." and $filename != ".." and $filename != ".svn" and $filename != "index.html")
		{
			$name = str_replace(".jpg", "", $filename);
		
			if (($name + $aCfg['expiration']) < $now)
			{
				unlink($aCfg['img_path'].$filename);
			}
		}
	}
	closedir($current_dir);
		
		
	
    // create a empty image
    $img = imagecreatetruecolor($aCfg['img_width'], $aCfg['img_height']);

    // get a random color 
    $col = imagecolorallocate($img, rand(170, 255), rand(170, 255), rand(170, 255));

    // fill this image with the random color
    imagefill($img, 0, 0, $col);
    
    
	//  Create the spiral pattern
	$x_axis = rand(6, (360/$aCfg['length'])-16);			
	$y_axis = rand(6, $aCfg['img_height']);
	$grid_color = imagecolorallocate($img, 255, 182, 182);
	$theta		= 1;
	$thetac		= 7;
	$radius		= 20;
	$circles	    = 17;
	$points		= 20;
	for ($i = 0; $i < ($circles * $points) - 1; $i++)
	{
		$theta = $theta + $thetac;
		$rad = $radius * ($i / $points );
		$x = ($rad * cos($theta)) + $x_axis;
		$y = ($rad * sin($theta)) + $y_axis;
		$theta = $theta + $thetac;
		$rad1 = $radius * (($i + 1) / $points);
		$x1 = ($rad1 * cos($theta)) + $x_axis;
		$y1 = ($rad1 * sin($theta )) + $y_axis;
		imageline($img, $x, $y, $x1, $y1, $grid_color);
		$theta = $theta - $thetac;
	}
	
	
    // the x-coordinate of the first char
    $x = 10; 

    // draw the chars
    for($i = 0; $i < $aCfg['length']; $i++) 
    {
        // get the current processed char from the word
        $chr = substr($aCfg['word'], $i, 1);
        
        // get a random color
        $col = imagecolorallocate($img, rand(0, 199), rand(0, 199), rand(0, 199)); 
        
        // get a random font from the list
        $font = $aCfg['fonts'][rand(0, count($aCfg['fonts']) - 1)]; 
        $font = $aCfg['font_path'].$font;

        // set the y-coordinate plus a random-value
        $y = 20 + rand(0, 10); 
        
        // get a random angle between 0 and 50 degrees
        $angle = rand(0, 50); 

        // check whether to use the current font or not...
        $use_font = ($font != '' AND file_exists($font) AND function_exists('imagettftext')) ? TRUE : FALSE;
        
        if ($use_font == FALSE)
		{
		    // draw a normal character to the image, not using TTF
			imagestring($img, $aCfg['font_size'], $x, $y, $chr, $col);
            
			$x += 20;
		}
		else
		{		
			// draw the char with the color and angle into the image , using a font
            imagettftext($img, $aCfg['font_size'], $angle, $x, $y, $col, $font, $chr);
            
            // calculate the dimensions of the char
            $dim = @imagettfbbox($aCfg['font_size'], $angle, $font, $chr);
        
            // set the new x-coordinate to the calculated width of the chars + a value
            $x += $dim[4] + abs($dim[6]) + 4;
		}
    }
    
	//  Create the border
	$border_color	= imagecolorallocate ($img, 153, 102, 102);
	imagerectangle($img, 0, 0, $aCfg['img_width']-1, $aCfg['img_height']-1, $border_color);		

	//  Generate the image
	$img_name = $now.'.jpg';
	ImageJPEG($img, $aCfg['img_path'].$img_name);
	
	$imgHtml = "<img src=\"".$aCfg['img_url'].$img_name."\" width=\"".$aCfg['img_width']."\" height=\"".$aCfg['img_height']."\" class=\"nb\" alt=\"\" id=\"t_".$now."\" />";

    ImageDestroy($img);
		
	return array('word' => $aCfg['word'], 'time' => $now, 'image' => $imgHtml);
}
?>