使用Codeigniter上传图像时如何在图像上添加水印？

Question

我正在上传图片，当时我还想添加水印图片。

我正在使用Ajax功能上传图片。

怎么做？

代码：

$this->load->library('upload');
            $this->load->library('image_lib');
            $config['image_library'] = 'GD2';
            $id = $_POST['id'];
            $UPLD_PATH = $this->admin_model->UPLD_PATH($id);
            $config['upload_path'] = './application/assets/images/' . $UPLD_PATH;
            $config['file_name'] = date('dmYHis');
            $config['allowed_types'] = 'gif|jpg|png|mp4|ogv|zip';
            $config['wm_overlay_path'] ='./application/assets/images/example.gif';
            $config['wm_text'] = 'Copyright ' . date('y') . ' - example.com';
            $config['wm_type'] = 'overlay';
            $config['wm_font_path'] = './application/assets/fonts/fontawesome-webfont.ttf';
            $config['wm_font_size'] = '16';
            $config['wm_opacity'] = '50';
            $config['wm_font_color'] = 'ffffff';
            $config['wm_vrt_alignment'] = 'bottom';
            $config['wm_hor_alignment'] = 'center';
            $config['wm_padding'] = '20';
            $this->upload->initialize($config);
            $this->load->library('upload', $config);
            if (!is_dir($config['upload_path'])) {
                mkdir($config['upload_path'], 0777, true);
            }
            $this->image_lib->initialize($config);

            $this->image_lib->watermark();
            $files = $_FILES;

            $number_of_files = count($_FILES['file']['name']);
            $errors = 0;