public function index()
    {
        $config['image_library'] = 'gd2';
         $this->load->library('image_lib', $config);
        $vals = array(
                'img_path'   => './captcha/',
                'img_url'    => base_url().'public/img/captcha/',
                'img_width'  => '200',
                'img_height' => 30,
                'border' => 0,
                'expiration' => 7200,
                );

                 // create captcha image
                $cap = create_captcha($vals);
                print_r($cap);
                // store image html code in a variable
                $arrData['image'] = $cap['image'];

               // store the captcha word in a session
                $this->session->set_userdata('word', $cap['word']);
        $arrData['middle'] = 'contact';
        $this->load->view('template',$arrData);
    }

<div class="enquiry-deatils">
          <label>Type character * :</label>
          <input type="text" placeholder="" class="captcha"/>
          <label><img src="images/capcha.jpg" /></label>
          <?php echo $image;  // this will show the captcha image ?>
        </div>

$vals = array(
            'img_path'   => 'mysite/public/img/captcha/',
            'img_url'    => 'mysite/public/img/captcha/',
            'img_width'  => '150',
            'img_height' => 30,
            'expiration' => 7200,
            "time" => time()
            );