public function add() {
    $path = 'img/noticias/';

    $config = array(
        'upload_path' => "./img/noticias/",
        'allowed_types' => "jpg|png|jpeg",
        'overwrite' => TRUE,
        'max_size' => "2048000",
        'max_height' => "768",
        'max_width' => "1024"
    );
    $this->load->library('upload', $config);

    if (!$this->upload->do_upload('addImage')) {
        $mensaje = array('error' => $this->upload->display_errors());
        die($mensaje['error']);
    }
    $file_info = $this->upload->data('addImage');
    $file_name = $file_info['file_type'];
    $datos = array(
        'autor' => $this->input->post('addAutor'),
        'nombre' => $this->input->post('addNombre'),
        'ruta' => $path.$file_name,
        'link' => $this->input->post('addLink')
    );
    echo "Nombre: ".$file_name;
    die();
    $resultado = $this->Articulos_Model->agregaArticulo($datos);
    if ($resultado) {
        redirect('index.php/Articulos', 'refresh');
    }


}

<!-- Add Modal-->
  <div class="modal fade" id="addModal" tabindex="-1" role="dialog" aria-labelledby="editaArticulo" aria-hidden="true">
   <div class="modal-dialog" role="document">
    <div class="modal-content">

        <?php echo form_open_multipart('index.php/Articulos/add'); ?>
       <div class="modal-header">
        <h5 class="modal-title text-center" id="editaArticulo">Agregar Artículo</h5>
        <button class="close" type="button" data-dismiss="modal" aria-label="Close">
          <span aria-hidden="true">×</span>
        </button>
      </div>
      <div class="modal-body">

        <div class="form-group">
          <div class="form-label-group">
            <input name="addAutor" type="text" id="addAutor" class="form-control" placeholder="Autor" required="required" autofocus="autofocus">
            <label for="addAutor">Autor</label>
          </div>
        </div>
        <div class="form-group">
          <div class="form-label-group">
            <input name="addNombre" type="text" id="addNombre" class="form-control" placeholder="Nombre Artículo" required="required" autofocus="autofocus">
            <label for="addNombre">Nombre Artículo</label>
          </div>
        </div>
        <div class="form-group">

         <label for="addFile">Eligir imagen</label>
         <input name="addImage" type="file" class="form-control-file" id="addFile" accept="image/png,image/jpg,image/jpeg">

       </div>
       <div class="form-group">
        <div class="form-label-group">
          <input name="addLink" type="text" id="addLink" class="form-control" placeholder="Link del Artículo" required="required" autofocus="autofocus">
          <label for="addLink">Link del Artículo</label>
        </div>
      </div>

      </div>
      <div class="modal-footer">
        <button class="btn btn-secondary" type="button" data-dismiss="modal">Cancel</button>
        <button class="btn btn-success" type="submit">Añadir</button>
      </div>
      <?php echo form_close(); ?>

  </div>
</div>