手機端將 圖片加入浮水印之後再儲存到手機本地
現在看到的下載怎麼都是下載到伺服器，不能下載到手機本地嗎？
下載程式碼參考了這個

    public function downloadImage($url, $path='images/')
    {
        $ch = curl_init();
        curl_setopt($ch, CURLOPT_URL, $url);
        curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
        curl_setopt($ch, CURLOPT_CONNECTTIMEOUT, 30);
        $file = curl_exec($ch);
        curl_close($ch);
        $this->saveAsImage($url, $file, $path);
    }

    private function saveAsImage($url, $file, $path)
    {
        $filename = pathinfo($url, PATHINFO_BASENAME);
        $resource = fopen($path . $filename, 'a');
        fwrite($resource, $file);
        fclose($resource);
    }