C#とPython間で画像を受け渡す【クラス】

    public class RestClient
    {

        private static readonly string BASE_URL = "http://localhost:5000";

        private HttpClient client = new HttpClient();

        public RestClient()
        {
            
        }

        public async Task<S> PostAsync<F, S>(F reqData)
        {
            string url = $"{BASE_URL}/api/data";
            var requestData = reqData;

            var jsonOptions = new JsonSerializerOptions
            {
                //WriteIndented = true
            };
            string jsonString = JsonSerializer.Serialize(requestData, jsonOptions);
            var content = new StringContent(jsonString, Encoding.UTF8, "application/json");

            HttpResponseMessage response = await client.PostAsync(url, content);
            if (response.IsSuccessStatusCode == false)
            {
                return default(S);
            }

            string responseBody = await response.Content.ReadAsStringAsync();
            S res = JsonSerializer.Deserialize<S>(responseBody, jsonOptions);

            //Console.WriteLine(responseBody);

            return res;
        }

    public class tModel
    {
        public string command { get; set; } = "";
        public string img_b64 { get; set; } = "";
        public string result { get; set; } = "";
    }

        private RestClient restClient = new RestClient();

        private async void buttonCommTest_Click(object sender, EventArgs e)
        {

            Rectangle screenRect = Program.App.Param.Regions[0]; // 画面上の領域
            using (Bitmap bmp = this.CaptureScreen(screenRect))
            {
                tModel req = new tModel();
                req.img_b64 = Base64Encoder.EncodeBitmap(bmp);　//画像をBase64文字列に変換
                tModel res = await this.restClient.PostAsync<tModel, tModel>(req);
                await Console.Out.WriteLineAsync(res.command);
                using (Bitmap resImage = Base64Encoder.DecodeBitmap(res.img_b64))
                {
                    //resImage.Show(this);
                }
            }
        }

from flask import Flask, jsonify, request

# POSTリクエストに対するルートエンドポイント
@app.route('/api/data', methods=['POST'])
def post_api_data():
    request_data = request.get_json()

    img_b64 = request_data['img_b64']
    image : any = Base64Encoder.DecodeImage(img_b64)
    #cv2.imwrite("target.png",image)

    result : str = "";

    # リクエストからデータを取得して処理する
    response_data = request_data;
    b64_str : str = Base64Encoder.EncodeImage(image)
    response_data['img_b64'] = b64_str
    response_data['result'] = result

    #print(response_data)
    return jsonify(response_data)

if __name__ == '__main__':
    app.run(host='0.0.0.0', port=5000)