C#生成验证码

  public static byte[] GetVerifyCode(string codeStr)
        {
            Random r = new Random();
            Bitmap btBitmap = new Bitmap(80, 30);

            Graphics g = Graphics.FromImage(btBitmap);
            g.Clear(Color.White);
            //画干扰线
            for (int i = 0; i < 20; i++)
            {
                int x1 = r.Next(btBitmap.Width);
                int y1 = r.Next(btBitmap.Height);
                int x2 = r.Next(btBitmap.Width);
                int y2 = r.Next(btBitmap.Height);
                g.DrawLine(new Pen(Color.Black),x1,y1,x2,y2 );
            }
            //画干扰点
            for (int i = 0; i < 100; i++)
            {
                int x1 = r.Next(btBitmap.Width);
                int y1 = r.Next(btBitmap.Height);
                btBitmap.SetPixel(x1,y1,Color.Aqua);
            }
            //画图
            g.DrawString(codeStr, new Font("宋体", 16), new SolidBrush(Color.Red), 0, 0);
            MemoryStream ms = new MemoryStream();
            btBitmap.Save(ms, ImageFormat.Gif);
            return ms.ToArray();
        }