C# 验证码2

 /// <summary>
    /// 验证码生成
    /// </summary>
    public class VerificationCodeHelper
    {
        //定义颜色 
        private static Color[] colors = { Color.Black, Color.Red, Color.DarkBlue, Color.Green, Color.Orange, Color.Brown, Color.DarkCyan, Color.Purple };
        //定义字体
        private static string font = "宋体";
        //定义验证码字符及出现频次 ,避免出现0 o j i l 1 x;  
        private static String charCollection = "ASDFGHZCVBNMKQWERTYUP";
        //字体大小
        private static int fontSize = 23;
        //旋转角度
        private static int angle = 30;


        /// <summary>
        /// 验证码生成
        /// </summary>
        /// <param name="guid">缓存标识</param>
        /// <param name="length">字符个数</param>
        /// <param name="width">宽度</param>
        /// <param name="height">高度</param>
        /// <returns></returns>
        public static byte[] GetBitmapCode(string guid, int width, int height, int length = 4)
        {
            //lk：这里高宽需要写死 或限制最大高宽 避免被攻击者写的太大导致内存占用过高
            height = height > 500 ? 500 : height;
            width = width > 500 ? 500 : width; 

            string codes = "";
            string code;
            int codeX = width / (length + 1);
            Random random = new Random();
            using (Bitmap image = new Bitmap(width, height))
            {
                using (Graphics g = Graphics.FromImage(image))
                {
                    //清空图片背景色 
                    g.Clear(Color.FromArgb(247, 247, 247));
                    g.FillRectangle(new SolidBrush(Color.FromArgb(247, 247, 247)), 0, 0, image.Width, image.Height);
                    //画图片的背景噪音线 
                    for (int i = 0; i < 5; i++)
                    {
                        g.DrawLine(new Pen(colors[random.Next(colors.Length)]), random.Next(image.Width), random.Next(image.Height), random.Next(image.Width), random.Next(image.Height));
                    }


                    //文字距中  
                    StringFormat format = new StringFormat(StringFormatFlags.NoClip);
                    format.Alignment = StringAlignment.Center;
                    format.LineAlignment = StringAlignment.Near;

                    using (Font f = new Font(font, fontSize, FontStyle.Regular))
                    {
                        using (Brush b = new SolidBrush(colors[random.Next(colors.Length)]))
                        {
                            for (int i = 0; i < length; i++)
                            {
                                code = charCollection[random.Next(0, charCollection.Length)].ToString();
                                SizeF sizeF = g.MeasureString(code, f);
                                PointF dot = new PointF(codeX, random.Next(image.Height / 3));

                                g.TranslateTransform(dot.X, dot.Y);//移动光标到指定位置  
                                int rAngel = random.Next(-angle, angle);
                                g.RotateTransform(rAngel);


                                g.DrawString(code, f, b, 1, 1, format);

                                g.RotateTransform(-rAngel);//转回去  
                                g.TranslateTransform(2, -dot.Y);//移动光标到指定位置  

                                codes += code;
                            }
                        }
                    }
                    //返回图片数据
                    using (System.IO.MemoryStream ms = new System.IO.MemoryStream())
                    {
                        image.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);
                        SaveToChache(guid, codes);
                        return ms.ToArray();
                    }
                }
            }
        }



        /// <summary>
        /// 保存验证码到内存中
        /// </summary>
        /// <param name="cacheFlag"></param>
        /// <param name="code"></param>
        public static void SaveToChache(string cacheFlag, string code)
        {
            string cacheName = RedisHelper.GetCacheName(RedisCacheType.VerificationCode, cacheFlag);
            CacheManager.SetCache(cacheName, code, TimeSpan.FromMinutes(5), ExpirType.Absolute);
        }

        /// <summary>
        /// 验证验证码是否正确
        /// </summary>
        /// <param name="cacheFlag"></param>
        /// <param name="code"></param>
        /// <returns></returns>
        public static string CheckCode(string cacheFlag, string code)
        {
            string cacheName = RedisHelper.GetCacheName(RedisCacheType.VerificationCode, cacheFlag);
            string cacheCode = CacheManager.GetCache(cacheName);
            if (string.IsNullOrEmpty(cacheCode))
            {
                return "验证码已过期，请重新输入！";
            }
            else
            {
                CacheManager.RemoveCache(cacheName);
                if (cacheCode.Equals(code, StringComparison.OrdinalIgnoreCase) == false)
                {
                    return "验证码错误，请重新输入！";
                }
                return null;
            }
        }
    }