edit iamges

$photo = $this->model_front->check_photo($id_foto); //here is check images by id
if ($photo->num_rows() > 0) //check images is already exist
{
   unlink("uploads/product/$row->foto"); //i delete the old images
   $this->db->delete('li_product_foto', array('id_foto' => $id_foto)); //deete data


//your default setting, i use codeigntier
//here is insert data again not update but same actually

$config['upload_path'] = './uploads/product/';
$config['allowed_types'] = 'gif|jpg|png';
$config['overwrite'] = FALSE;
$config['max_size'] = '500000';
$this->upload->initialize($config);
if ($this->upload->do_upload('file')) {
    $upload_data = $this->upload->data();
    $fileName = $upload_data['file_name'];
    $this->load->library('image_lib');
    $config['image_library'] = 'gd2';
    $config['source_image'] = $this->upload->upload_path.$this->upload->file_name;
        $config['create_thumb'] = FALSE;
    $config['height'] = 250;
    $config['width'] = 350;
    $config['new_image'] = "./uploads/product/";//you should have write permission here..
    $this->image_lib->initialize($config);
    $this->image_lib->resize();
    $data=array('foto'=>$fileName,
            'id_product_post'=>$this->input->post('id_product_post_edit'),
            'is_used'=>'1'
 $this->model_front->addfoto($data);
}