public function capture($url)
    {
        $this->setUrl($url);

        $client = new Client();
        $response = $client->post($this->apiUrl, ['form_params' =>
            [
                'key'    => $this->key,
                'url'    => $url,
                'width'  => $this->width,
                'height' => $this->height
            ]
        ]);

        $responseJson =  $response->getBody();
        $responseArray = json_decode($responseJson);

        $this->response = $responseArray;

        return $this;
    }