Captcha Image in PHP

• Download Confirm_image.zip - 3.38 KB

Introduction

You can use this class to increase your web's form security and perevent auotomatic registration.

Using the code

First we need to write a class to generates random characters
DayyanRandomCharacters Class generates random character :

class DayyanRandomCharacters
{
    private $id;
    private $key_str;
    private $Code;//Orginal string code

////////////////////////////////////////////////////////////////////////////////

    public function __construct()
    {
        $this -> create();
    }

////////////////////////////////////////////////////////////////////////////////

    public function get_code()
    {
        return $this -> Code;
    }

////////////////////////////////////////////////////////////////////////////////

    private function create()
    {
        $string = "";
        $string = md5(rand(0, microtime() * 1000000));
        $this-> id = $this-gtCode   = substr($string, 3, 6);
        $this-> key_str = md5(rand(0, 999));
    }

////////////////////////////////////////////////////////////////////////////////

    private function get_rnd_iv($iv_len)
    {
        $iv = '';
        while ($iv_len-- > 0) {
            $iv .= chr(mt_rand() 0xff);
        }
        return $iv;
    }

////////////////////////////////////////////////////////////////////////////////

    public function get_id()
    {

        return urlencode($this -> md5_encrypt($this-gtid, $this-gtkey_str));
    }

////////////////////////////////////////////////////////////////////////////////

    public function get_key()
    {
        return $this -> key_str;
    }

////////////////////////////////////////////////////////////////////////////////
    //encrypt id 
    private function md5_encrypt($plain_text, $password, $iv_len = 16)
    {
        $plain_text .= "x13";
        $n = strlen($plain_text);
        if ($n % 16) $plain_text .= str_repeat("0", 16 - ($n % 16));
        $i = 0;
        $enc_text = $this -> get_rnd_iv($iv_len);
        $iv = substr($password ^ $enc_text, 0, 512);
        while ($i < $n)
        {
            $block = substr($plain_text, $i, 16) ^ pack('H*', md5($iv));
            $enc_text .= $block;
            $iv = substr($block . $iv, 0, 512) ^ $password;
            $i += 16;
        }
        return base64_encode($enc_text);
    }

////////////////////////////////////////////////////////////////////////////////

    public function md5_decrypt($enc_text, $password, $iv_len = 16)
    {
        $enc_text = base64_decode($enc_text);
        $n = strlen($enc_text);
        $i = $iv_len;
        $plain_text = '';
        $iv = substr($password ^ substr($enc_text, 0, $iv_len), 0, 512);
        while ($i < $n)
        {
            $block = substr($enc_text, $i, 16);
            $plain_text .= $block ^ pack('H*', md5($iv));
            $iv = substr($block . $iv, 0, 512) ^ $password;
            $i += 16;
        }
        return preg_replace('/\\x13\\x00*$/', '', $plain_text);
    }
}

 

OK, now we can get encrypted id and key with this code :

    $DayyanRandomCharacters = new DayyanRandomCharacters();
    $id = $DayyanRandomCharacters -> get_id();
    $key = $DayyanRandomCharacters -> get_key();
    $Code = $DayyanRandomCharacters -> get_code();//Orginal String code

Now we have to write a class to generates CAPTCHA image : DayyanConfirmImageClass.php
This class can use above random characters to generate CAPTCHA image.

---

DayyanConfirmImageClass.php's fields :

    private $showLine; // whether show line for windows image
    private $Characters; // random characters
    //colors' code to fill background
    private $Colors =  array (    '0' => '145',
                                '1' => '204',
                                '2' => '177',
                                '3' => '184',
                                '4' => '199',
                                '5' => '255');
                                

DayyanConfirmImageClass.php's methods :

__construct : Constructor of class

    public function __construct($ConfirmCode)
    {
        //Show lines in output image
        $this -> showLine = true; 
        
        //this class generates image with this characters
        $this -> Characters = $ConfirmCode; 
    }

ShowLine : Assigned $this -> showLine with $value

    public function ShowLine($value=false)
    {
        $this -> showLine = $value;
    }

ShowImage : Detected server operation and called $this -> win(); or $this -> linux();
because we don't have font like "tahomabd" in linux I used this function

    public function ShowImage()
    {
        //detect server operation system
        if ( strtoupper(substr(PHP_OS, 0, 3)) === 'WIN' )    //windows detected
            $this -> win();
        else    //linux detected
            $this -> linux();
    }

win : Generate CAPTCHA image for windows

    private function win()
    {
        ////////////////////////////////////
        //background image
        $image = imagecreatetruecolor(320, 50) or 
            die("<b>". __FILE__ . "</b><br />" . __LINE__ . " : " 
                ."Cannot Initialize new GD image stream");
        $bg = imagecolorallocate($image, 255, 255, 255);
        imagefill($image, 10, 10, $bg);

        //generate black and white background
        for ($x=0; $x < 320; $x++)
        {
            for ($y=0; $y < 50; $y++)
            {
                $random = mt_rand(0 , 5);
                $temp_color = imagecolorallocate($image, $this -> 
                Colors["$random"], $this -> Colors["$random"], 
                $this -> Colors["$random"]);
                imagesetpixel( $image, $x, $y , $temp_color );
            }
        }

        //Characters color
        $char_color = imagecolorallocatealpha($image, 0, 0, 0, 90);

        //Font
        $font = "tahomabd";

        ////////////////////////////////////
        //Draw characters

        $char = "";

        $char = $this -> Characters[0];
        $random_x = mt_rand(10 , 20);
        $random_y = mt_rand(35 , 45);
        $random_angle = mt_rand(-20 , 20);
        imagettftext($image, 30, $random_angle, $random_x, 
            $random_y, $char_color, $font, $char);



        $char = $this -> Characters[1];
        $random_x = mt_rand(50 , 70);
        $random_y = mt_rand(35 , 45);
        $random_angle = mt_rand(-20 , 20);
        imagettftext($image, 30, $random_angle, $random_x, 
            $random_y, $char_color, $font, $char);



        $char = $this -> Characters[2];
        $random_x = mt_rand(100 , 120);
        $random_y = mt_rand(35 , 45);
        $random_angle = mt_rand(-20 , 20);
        imagettftext($image, 30, $random_angle, $random_x, 
            $random_y, $char_color, $font, $char);


        $char = $this -> Characters[3];
        $random_x = mt_rand(150 , 170);
        $random_y = mt_rand(35 , 45);
        $random_angle = mt_rand(-20 , 20);
        imagettftext($image, 30, $random_angle, $random_x, 
            $random_y, $char_color, $font, $char);


        $char = $this -> Characters[4];
        $random_x = mt_rand(200 , 220);
        $random_y = mt_rand(35 , 45);
        $random_angle = mt_rand(-20 , 20);
        imagettftext($image, 30, $random_angle, $random_x, 
            $random_y, $char_color, $font, $char);


        $char = $this -> Characters[5];
        $random_x = mt_rand(250 , 270);
        $random_y = mt_rand(35 , 45);
        $random_angle = mt_rand(-20 , 20);
        imagettftext($image, 30, $random_angle, $random_x, 
            $random_y, $char_color, $font, $char);

        ////////////////////////////////////
        //Image lines
        if ($this -> showLine)
        {
            for ($i=0; $i<320; $i++ )
            {
                if ($i%10 == 0)
                {
                    imageline ( $image, $i, 0, $i+10, 50, $char_color );
                    imageline ( $image, $i, 0, $i-10, 50, $char_color );
                }
            }
        }

        ////////////////////////////////////
        return imagepng($image); //return image
        imagedestroy($image); //frees any memory associated with $image
    }

linux : Generate CAPTCHA image for linux like above function

    private function linux()
    {
        ////////////////////////////////////
        //Background image
        $image = imagecreatetruecolor(150, 50) or 
            die("<b>" . __FILE__ . "</b><br />" . __LINE__ . " : " 
                ."Cannot Initialize new GD image stream");
        $bg = imagecolorallocate($image, 255, 255, 255);
        imagefill($image, 10, 10, $bg);

        //generate black and white background
        for ($x=0; $x < 150; $x++)
        {
            for ($y=0; $y < 50; $y++)
            {
                $random = mt_rand(0 , 5);
                $temp_color = 
                imagecolorallocate($image, $this -> Colors["$random"], 
                $this -> Colors["$random"], $this -> Colors["$random"]);
                imagesetpixel( $image, $x, $y , $temp_color );
            }
        }
        
        //Characters color
        $char_color = imagecolorallocatealpha($image, 0, 0, 0, 60);

        ////////////////////////////////////
        //Image Info
        $font = 5;

        ////////////////////////////////////
        //Draw characters

        $char = $this -> Characters[0];
        $random_x = mt_rand(10 , 20);
        $random_y = mt_rand(15,25);
        imagestring($image, $font, $random_x, 
            $random_y, $char, $char_color);



        $char = $this -> Characters[1];
        $random_x = mt_rand(30 , 40);
        $random_y = mt_rand(15,25);
        imagestring($image, $font, $random_x, 
            $random_y, $char, $char_color);



        $char = $this -> Characters[2];
        $random_x = mt_rand(50 , 60);
        $random_y = mt_rand(15,25);
        imagestring($image, $font, $random_x, 
            $random_y, $char, $char_color);


        $char = $this -> Characters[3];
        $random_x = mt_rand(70 , 80);
        $random_y = mt_rand(15,25);
        imagestring($image, $font, $random_x, 
            $random_y, $char, $char_color);


        $char = $this -> Characters[4];
        $random_x = mt_rand(90 , 100);
        $random_y = mt_rand(15,25);
        imagestring($image, $font, $random_x, 
            $random_y, $char, $char_color);


        $char = $this -> Characters[5];
        $random_x = mt_rand(110 , 120);
        $random_y = mt_rand(15,25);
        imagestring($image, $font, $random_x, 
            $random_y, $char, $char_color);

        ///////////////////////
        return imagepng($image); //return image
        imagedestroy($image); //frees any memory associated with $image
    }

---

Now we have to use above classes :
include/index.php : Generates and return image with $_REQUEST['id'] and $_REQUEST['key']

try
{
    include_once("DayyanConfirmImageClass.php");
    include_once("DayyanRandomCharactersClass.php");

    $id = (isset($_REQUEST['id'])  !empty($_REQUEST['id'])) 
            ? trim($_REQUEST['id']) : exit;
    $key = (isset($_REQUEST['key'])  !empty($_REQUEST['key'])) 
            ? trim($_REQUEST['key']) : exit;

    $DayyanRandomCharacters = new DayyanRandomCharacters();
            //encrypt string
    $ConfirmString = 
        strtoupper($DayyanRandomCharacters -> md5_decrypt($id, $key));

    $DayyanConfirmImage = new DayyanConfirmImage($ConfirmString);
    $DayyanConfirmImage -> ShowLine(false);
    $DayyanConfirmImage -> ShowImage();
}
catch(Exception $ex)
{
    echo 'Caught exception: ',  $e -> getMessage(), '\n';
    exit;
}

index.php : Generates random characters and send $_REQUEST['id'] and $_REQUEST['key'] for generete image.

include_once("include/DayyanRandomCharactersClass.php");

try
{
    $DayyanRandomCharacters = new DayyanRandomCharacters();
    $id = $DayyanRandomCharacters -> get_id();
    $key = $DayyanRandomCharacters -> get_key();
    $Code = $DayyanRandomCharacters -> get_code();
}
catch(Exception $ex)
{
    echo 'Caught exception: ',  $e -> getMessage(), "<br />";
    exit;
}

Now with IMG tag we can see result :

<img src="include/?id=<?php echo $id;?>
    key=<?php echo $key; ?>" 
    alt="Dayyan Confirm Image" title="Dayyan Confirm Image" 
    name="DayyanConfirmImage" border="0" id="DayyanConfirmImage" />



<input name="Code" type="text" id="Code" value="<?php echo $Code ?>" />

Enjoy !

History

Friday, June 13, 2008 : Fixed bug ( reported by signuperror )

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Subject   Author  Date  Very useful Perspx 14:46 6 Aug '08   Nice work Regards, --Perspx "The Blue Screen of Death, also known as The Blue Screen of Doom, the "Blue Screen of Fun", "Phatul Exception: The WRECKening" and "Windows Vista", is a multi award-winning game first developed in 1995 by Microsoft" - Uncyclopedia Sign In·View Thread·PermaLink 5.00/5 (1 vote) Re: Very useful Mohammad Dayyan 15:24 6 Aug '08   Thank you Sign In·View Thread·PermaLink but... [modified] signuperror 4:20 12 Jun '08   thanks for writing and sharing this. it is very slick, but it is still pretty easily bot'able due to the img line in the generated html. for example, this is generated when the image and confirm code are "2391BA": img src="include/?ConfirmCode=2391BA" alt="Dayyan Confirm Image" title="Dayyan Confirm Image" name="DayyanConfirmImage" border="0" id="DayyanConfirmImage" /> do you have an idea for passing the request in such a way that it doesn't show in the img tag line? i had success using session_create() in both index.php files, set $_SESSION['confString'] in index.php and use $_SESSION['confString'] in include/index.php. i actually need to store the confString for later use after the user types it in and clicks "submit". W modified on Thursday, June 12, 2008 10:37 AM Sign In·View Thread·PermaLink 5.00/5 (1 vote) Re: but... M-Dayyan 11:10 12 Jun '08   Ohhh Thanks signuperror you're right. I'm thinking the best way is your way. But I'll try to fix it. Sorry for my English. I'm a freshman . Sign In·View Thread·PermaLink Re: but... [modified] M-Dayyan 14:25 12 Jun '08   I fixed it, you can try it. Thanks for your notice. Sorry for my English. I'm a freshman . modified on Saturday, June 14, 2008 3:42 AM Sign In·View Thread·PermaLink Thanks Dayyan Hari Om Prakash Sharma 1:30 6 Jun '08   This article helps me a lot..! First and the Foremost: FIGHT TO WIN MySite: HariOmPrakash.InFo Sign In·View Thread·PermaLink 5.00/5 (1 vote) Re: Thanks Dayyan M-Dayyan 2:22 6 Jun '08   Don't mention it. Sorry for my English. I'm a freshman . Sign In·View Thread·PermaLink 1.00/5 (1 vote)

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