c# core 生成随机图文验证码

 //随机生成常用的汉字

public string GenerateChineseWords()
        {
            int count = 100;
            string chineseWords = "";
            Random rm = new Random();
            Encoding gb = Encoding.GetEncoding("gb2312");

            for (int i = 0; i < count; i++)
            {
                // 获取区码(常用汉字的区码范围为16-55)   
                int regionCode = rm.Next(16, 56);
                // 获取位码(位码范围为1-94 由于55区的90,91,92,93,94为空,故将其排除)   
                int positionCode;
                if (regionCode == 55)
                {
                    // 55区排除90,91,92,93,94   
                    positionCode = rm.Next(1, 90);
                }
                else
                {
                    positionCode = rm.Next(1, 95);
                }

                // 转换区位码为机内码   
                int regionCode_Machine = regionCode + 160;// 160即为十六进制的20H+80H=A0H   
                int positionCode_Machine = positionCode + 160;// 160即为十六进制的20H+80H=A0H   

                // 转换为汉字   
                byte[] bytes = new byte[] { (byte)regionCode_Machine, (byte)positionCode_Machine };
                chineseWords += gb.GetString(bytes);
            }

            return chineseWords;
        }

        

       /// <summary>  
        /// 随机获取汉字
        /// </summary>  
        /// <param name="number"></param>  
        /// <returns></returns>  
        private static string RandomHanZi(int number)
        {
            //获取常用中文
            ChineseCreator chineseCreator = new ChineseCreator();
            var str = chineseCreator.GenerateChineseWords();
            char[] str_char_arrary = str.ToArray();
            Random rand = new Random();
            HashSet<string> hs = new HashSet<string>();
            bool randomBool = true;
            while (randomBool)
            {
                if (hs.Count == number)
                    break;
                int rand_number = rand.Next(str_char_arrary.Length);
                hs.Add(str_char_arrary[rand_number].ToString());
            }
            string code = string.Join("", hs);
            return code;
        }

        /// <summary>
        /// 生成图文验证码
        /// </summary>
        /// <param name="numbers">生成位数（默认5位）</param>  
        /// <param name="_height">图片高度</param>  
        /// <param name="_width">图片宽度</param>  
        public object CreateHanZi(int numbers = 5, int _height = 200, int _width = 200)
        {
            //要选择的位数
            int choicenumber = 4;
            var imageModel = new VerificationCodeModel();
            try
            {
                string code = RandomHanZi(numbers);
                Bitmap Img = null;
                Graphics g = null;
                MemoryStream ms = null;
                Random random = new Random();

                Color[] color_Array = { Color.Black, Color.DarkBlue, Color.Green, Color.Orange, Color.Brown, Color.DarkCyan, Color.Purple,Color.HotPink ,Color.Fuchsia ,Color.GreenYellow ,Color.Aquamarine };

                string[] fonts = { "lnk Free", "Segoe Print", "Comic Sans MS", "MV Boli", "华文行楷" ,"微软雅黑","楷书"};

                string _base = Environment.CurrentDirectory + "\wwwroot\CodImage\";
        
                var _file_List = System.IO.Directory.GetFiles(_base);
                int imageCount = _file_List.Length;
                if (imageCount == 0)
                    throw new Exception("image not Null");

                int imageRandom = random.Next(1, (imageCount + 1));
                string _random_file_image = _file_List[imageRandom - 1];
                var imageStream = Image.FromFile(_random_file_image);

                Img = new Bitmap(imageStream, _width, _height);
                imageStream.Dispose();
                g = Graphics.FromImage(Img);
                Color[] penColor = { Color.LightGray, Color.Green, Color.Blue };
                int code_length = code.Length;
                for (int i = 0; i < code_length; i++)
                {
                    int cindex = random.Next(color_Array.Length);
                    int findex = random.Next(fonts.Length);
                    Font f = new Font(fonts[findex], 15, FontStyle.Bold);
                    Brush b = new SolidBrush(color_Array[cindex]);
                    int _y = random.Next(_height);
                    if (_y > (_height - 30))
                        _y = _y - 60;

                    int _x = _width / (i + 1);
                    if ((_width - _x) < 50)
                    {
                        _x = _width - 60;
                    }
                    string word = code.Substring(i, 1);
                    if (imageModel.point_X_Y.Count < choicenumber)
                    {
                        imageModel.point_X_Y.Add(new Point_X_Y()
                        {
                            Word = word,
                            _X = _x,
                            _Y = _y,
                            Sort = i,
                           
                    });
                    }
                    g.DrawString(word, f, b, _x, _y);
                }
                ms = new MemoryStream();
                Img.Save(ms, ImageFormat.Jpeg);
                g.Dispose();
                Img.Dispose();
                ms.Dispose();
                //生成验证码唯一id
                imageModel.CodeId = Guid.NewGuid().ToString("N");
                imageModel.ImageBase64Str = "data:image/jpg;base64," + Convert.ToBase64String(ms.GetBuffer());

            }
            catch (Exception e)
            {
                return Task.FromResult(new { result = "出错了", CodeId = "出错了", msg = "出错了" });

            }
            string msg = "请根据顺序点击【" + string.Join("", imageModel.point_X_Y.Select(m => m.Word).ToList()) + "】";
            //这是存到了redis 也可以存别的地
            TimeSpan second = TimeSpan.FromSeconds(ExpirationSecond);
            //_redis.StringSetAsync(RedisKeys.VerificationCode+":"+ imageModel.CodeId, imageModel.point_X_Y);
            _redis.StringSetAsync(RedisKeys.VerificationCode + ":" + imageModel.CodeId, imageModel.point_X_Y, second);

            return new { result = imageModel.ImageBase64Str, CodeId = imageModel.CodeId, msg = msg };
        }

//验证验证码是否正确
public async Task<LoginRes> VerificationCodeAsync(string codeId,List<Point_X_Y> point) {

            List<Point_X_Y> getRedisCode;
            var resOk = new LoginRes
            {

                code =20000,
                msg = "验证成功"
            };
            var resErro = new LoginRes
            {

                code = 50000,
                msg = "验证失败"
            };
            try
            {
                //验证失败
                if (point.Count != choicenumber)
                    return resErro;

                getRedisCode = await _redis.StringGetAsync<List<Point_X_Y>>(RedisKeys.VerificationCode + ":" + codeId);
                
               
                //验证失败
                if (getRedisCode.Count() == 0)
                    return resErro;
            
                //验证选择
                for (int i = 0; i < getRedisCode.Count(); i++)
                {
                    var vefA = getRedisCode.Where(m => m.Sort == i).ToList();
                    var vefB = point.Where(m => m.Sort == i).ToList();
                    int _x = vefA.FirstOrDefault()._X - vefB.FirstOrDefault()._X;
                    int _y = vefA.FirstOrDefault()._Y - vefB.FirstOrDefault()._Y;
                    string _w = vefA.FirstOrDefault().Word;
                    string _m = vefA.FirstOrDefault().Word;
                    _x = Math.Abs(_x);
                    _y = Math.Abs(_y);
                    if (_x > 25 || _y > 25 || _w != _m)
                    {
                        return resErro;
                    }
                }
                //将验证码从redis移除
                _redis.Remove(RedisKeys.VerificationCode + ":" + codeId);
                return resOk;
            }
            catch (Exception)
            {
                _redis.Remove(RedisKeys.VerificationCode + ":" + codeId);
                return resErro;
            }

生成如下图的验证码