腾讯云图片鉴黄集成到C#

官方文档：https://cloud.tencent.com/document/product/641/12422

请求官方API及签名的生成代码如下：

    public class TencentCloundPicHelper
    {
        /// <summary>
        /// 发送Post请求腾讯云
        /// </summary>
        public string SendPost(string postDataStr)
        {
            var url = @"http://service.image.myqcloud.com/detection/porn_detect";

            try
            {
                System.Net.ServicePointManager.Expect100Continue = false;
                var request = (HttpWebRequest)HttpWebRequest.Create(url);
                
                request.Method = "POST";
                
                SetHeaderValue(request.Headers, "content-type", "application/json");
                SetHeaderValue(request.Headers, "content-length", postDataStr.Length.ToString());
                SetHeaderValue(request.Headers, "Host", "service.image.myqcloud.com");
                SetHeaderValue(request.Headers, "authorization", GetSign());
                var memStream = new MemoryStream();
                
                var jsonByte = Encoding.GetEncoding("utf-8").GetBytes(postDataStr);
                memStream.Write(jsonByte, 0, jsonByte.Length);

                request.ContentLength = memStream.Length;
                var requestStream = request.GetRequestStream();
                memStream.Position = 0;
                var tempBuffer = new byte[memStream.Length];
                memStream.Read(tempBuffer, 0, tempBuffer.Length);
                memStream.Close();

                requestStream.Write(tempBuffer, 0, tempBuffer.Length);
                requestStream.Close();

                var response = request.GetResponse();
                using (var s = response.GetResponseStream())
                {
                    var reader = new StreamReader(s, Encoding.UTF8);
                    return reader.ReadToEnd();
                }
            }
            catch (WebException we)
            {
                if (we.Status == WebExceptionStatus.ProtocolError)
                {
                    using (var s = we.Response.GetResponseStream())
                    {
                        var reader = new StreamReader(s, Encoding.UTF8);
                        return reader.ReadToEnd();
                    }
                }
                else
                {
                    throw we;
                }
            }
            catch (Exception e)
            {
                throw e;
            }
        }

        /// <summary>
        /// 获取签名
        /// </summary>
        public static string GetSign()
        {
            var appId = ConfigurationManager.AppSettings["AppId"];//开发者的 APPID，接入智能图像时由系统生成
            var bucket = "tengxunyun";//Bucket，空间名称，即图片资源的组织管理单元
            var secretId = ConfigurationManager.AppSettings["SecretId"];//Secret ID
            var secretKey = ConfigurationManager.AppSettings["SecretKey"];//secretKey
            var ts = DateTime.UtcNow - new DateTime(1970, 1, 1, 0, 0, 0, 0);
            var currentTime = Convert.ToInt64(ts.TotalSeconds);//当前时间戳，是一个符合 UNIX Epoch 时间戳规范的数值，单位为秒，多次签名时，e 应大于 t
            var expiredTime = Convert.ToInt64((DateTime.UtcNow.AddMinutes(180) - new DateTime(1970, 1, 1, 0, 0, 0, 0)).TotalSeconds);//签名的有效期，是一个符合 UNIX Epoch 时间戳规范的数值，单位为秒；单次签名时，e 必须设置为 0
            var rand = GetRandom();//随机串，无符号 10 进制整数，用户需自行生成，最长 10 位
            var userid = 0;//历史遗留字段，请填写为 0
            var fileid = "";//资源存储的唯一标识，单次签名必填；多次签名选填，如填写则会验证与当前操作的文件路径是否一致。
            var encryptText = $"a={appId}&b={bucket}&k={secretId}&e={expiredTime}&t={currentTime}&r={rand}&u=0&f=";
            var sign = Hmacsha1Encrypt(encryptText, secretKey);

            return sign;
        }

        /// <summary>
        /// 设置Http post请求头
        /// </summary>
        public static void SetHeaderValue(WebHeaderCollection header, string name, string value)
        {
            var property = typeof(WebHeaderCollection).GetProperty("InnerCollection", BindingFlags.Instance | BindingFlags.NonPublic);
            if (property != null)
            {
                var collection = property.GetValue(header, null) as NameValueCollection;
                collection[name] = value;
            }
        }

        /// <summary>
        /// HMACSHA1算法加密
        /// </summary>
        private static string Hmacsha1Encrypt(string encryptText, string encryptKey)
        {
            using (HMACSHA1 mac = new HMACSHA1(Encoding.UTF8.GetBytes(encryptKey)))
            {
                var hash = mac.ComputeHash(Encoding.UTF8.GetBytes(encryptText));
                var pText = Encoding.UTF8.GetBytes(encryptText);
                var all = new byte[hash.Length + pText.Length];
                Array.Copy(hash, 0, all, 0, hash.Length);
                Array.Copy(pText, 0, all, hash.Length, pText.Length);
                return Convert.ToBase64String(all);
            }
        }

        /// <summary>
        /// 获取随机数
        /// </summary>
        private static int GetRandom()
        {
            var random = new Random();
            var rand = random.Next(10000, 999999999);
            return rand;
        }
    }