error when i use resize() library in codeigniter -

i want resize image when controller receive fileimage view code

$this->load->library('upload'); $config[''image_library] = gd2;              $config['upload_path'] = $path ; $config['allowed_types'] = 'gif|jpg|png'; $config['max_size'] = '1024'; $config['max_width']  = '1024'; $config['max_height']  = '768'; $config['encrypt_name'] = 'true'; $config['width'] = 200; $config['height'] = 200; $this->upload->initialize($config); $this->upload->resize(); if(!$this->upload->resize()){    echo $this->upload->display_error(); } 

my error is

call undefined method ci_upload::resize() 

thank you

error : $config[''image_library] = gd2;

$config['image_library'] = gd2; 

load image manipulation class:

$this->load->library('image_lib', $config); 

error: $this->upload->resize(); if(!$this->upload->resize()){ echo $this->upload->display_error(); }

if( !$this->upload->do_upload() ){     print_r( $this->upload->display_errors() ); }else{     $this->image_lib->resize(); }