controller

public function upload_image(){
        $data['id_boat'] = $this->input->post('id_boat',TRUE);

        $temp_file_path = tempnam(sys_get_temp_dir(), 'androidtempimage'); // might not work on some systems, specify your temp path if system temp dir is not writeable
        file_put_contents($temp_file_path , base64_decode(preg_replace('#^data:image/\w+;base64,#i', '', $_POST['userfile'])));
        $image_info = getimagesize($temp_file_path);
        $_FILES['userfile'] = array(
             'name' => uniqid().'.'.preg_replace('!\w+/!', '', $image_info['mime']),
             'tmp_name' => $temp_file_path,
             'size'  => filesize($temp_file_path),
             'error' => UPLOAD_ERR_OK,
             'type'  => $image_info['mime']
         );

        $config['upload_path']          = './assets/images/boat/';
        $config['allowed_types']        =  'jpg|gif|png|jpeg|JPG|PNG';
        $config['max_size']             = 1000000;
        $config['max_width']            = 10240000;
        $config['max_height']           = 7680000;

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

        if ( ! $this->upload->do_upload('userfile',true))
        {
                $error = array('error' => $this->upload->display_errors(),
                                'file' => $_FILES['userfile']);
                echo json_encode($error);
        }
        else
        {
                $photo = $this->upload->data();
                $data['foto_boat'] = $photo['file_name'];
                $update = $this->Boat_model->simpan_ubah($data,$data['id_boat']);
                if($update){
                    $data['status'] = 'Berhasil ubah foto';
                }else{
                    $data['status'] = 'Gagal ubah foto';
                }
                echo json_encode($data);

        }
    }