C# 验证码2

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/// <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;
           }
       }
   }