netcore 获取验证码

public IActionResult CreateIntCode()
        {
            string code = new Random().Next(999999).ToString("000000");
            using (Bitmap image = new Bitmap(76, 32))
            {
                Random random = new Random();
                int min = 70, max = 170;
                Color bg;
                using (Graphics g = Graphics.FromImage(image))
                {
                    int bad = random.Next(3);//总有一个颜色分量可能偏深色
                    bg = Color.FromArgb(random.Next(bad == 0 ? 120 : 200, 255), random.Next(bad == 1 ? 120 : 200, 255), random.Next(bad == 2 ? 120 : 200, 255));
                    g.Clear(bg);
                    Font font = new Font("Arial", 18, FontStyle.Bold);
                    Color c1 = Color.FromArgb(random.Next(min, max), random.Next(min, max), random.Next(min, max));
                    Color c2 = Color.FromArgb(random.Next(min, max), random.Next(min, max), random.Next(min, max));
                    //字体由上到下颜色渐变
                    LinearGradientBrush brush = new LinearGradientBrush(new Rectangle(0, 0, 10, 22), c1, c2, 90, true);
                    int x = random.Next(-8, -1);
                    for (int i = 0; i < code.Length; i++)
                    {
                        Matrix transform = g.Transform;
                        //上下波动
                        transform.Shear(0, Convert.ToSingle((random.NextDouble() - 0.5) / 5));
                        g.Transform = transform;
                        x += random.Next(9, 11);
                        g.DrawString(code.Substring(i, 1), font, brush, x, 3);
                        g.ResetTransform();
                    }
                }
                using (Bitmap destBmp = new Bitmap(image.Width, image.Height))
                {
                    using (Graphics g = Graphics.FromImage(destBmp))
                    {
                        // 填充位图背景
                        g.FillRectangle(new SolidBrush(bg), 0, 0, destBmp.Width, destBmp.Height);

                        double dBaseAxisLen = (double)destBmp.Height;
                        double dPhase = 0;
                        for (int i = 0; i < destBmp.Width; i++)
                        {
                            //干扰线
                            //if ((i % 15) == 1) dPhase = random.NextDouble() * Math.PI * 2;
                            for (int j = 0; j < destBmp.Height; j++)
                            {
                                double dx = Math.PI * j * 2 / dBaseAxisLen + dPhase;
                                double dy = Math.Sin(dx);

                                // 取得当前点的颜色
                                int nOldX = i + (int)(dy * 3);
                                int nOldY = j;

                                Color color = image.GetPixel(i, j);
                                if (nOldX >= 0 && nOldX < destBmp.Width && nOldY >= 0 && nOldY < destBmp.Height)
                                {
                                    destBmp.SetPixel(nOldX, nOldY, color);
                                }
                            }
                        }
                        g.SmoothingMode = SmoothingMode.HighSpeed;
                    };
                    MemoryStream ms = new MemoryStream();
                    destBmp.Save(ms, System.Drawing.Imaging.ImageFormat.Bmp);
                    byte[] b = new byte[ms.Length];
                    ms.Position = 0;
                    ms.Read(b, 0, Convert.ToInt32(ms.Length));
                    ms.Close();
                    return File(b, "image/jpeg");
                }
            }
        }

code也可以用上一个的GetRandomString方法获取随机字符串后，做字符验证码，不过，转字符流的时候，用Image即可，destBmp有点难以识别。