/// <summary>
      /// 圖像灰度化
      /// </summary>
      /// <param name="bmp"></param>
      /// <returns></returns>
      public static Bitmap ToGray(Bitmap bmp)
      {
          for (int i = 0; i < bmp.Width; i++)
          {
              for (int j = 0; j < bmp.Height; j++)
              {
                  //獲取該點的像素的RGB的顏色
                  Color color = bmp.GetPixel(i, j);
                  //利用公式計算灰度值
                  int gray = (int)(color.R * 0.3 + color.G * 0.59 + color.B * 0.11);
                  Color newColor = Color.FromArgb(gray, gray, gray);
                  bmp.SetPixel(i, j, newColor);
              }
          }
          return bmp;
      }

/// <summary>
      /// 圖像灰度反轉
      /// </summary>
      /// <param name="bmp"></param>
      /// <returns></returns>
      public static Bitmap GrayReverse(Bitmap bmp)
      {
          for (int i = 0; i < bmp.Width; i++)
          {
              for (int j = 0; j < bmp.Height; j++)
              {
                  //獲取該點的像素的RGB的顏色
                  Color color = bmp.GetPixel(i, j);
                  Color newColor = Color.FromArgb(255 - color.R, 255 - color.G, 255 - color.B);
                  bmp.SetPixel(i, j, newColor);
              }
          }
          return bmp;
      }

  /// <summary>
        /// 圖像二值化1：取圖片的平均灰度作為閾值，低于該值的全都為0，高于該值的全都為255
        /// </summary>
        /// <param name="bmp"></param>
        /// <returns></returns>
        public static Bitmap ConvertTo1Bpp1(Bitmap bmp)
        {
            int average = 0;
            for (int i = 0; i < bmp.Width; i++)
            {
                for (int j = 0; j < bmp.Height; j++)
                {
                    Color color = bmp.GetPixel(i, j);
                    average += color.B;                    
                }
            }
            average = (int)average / (bmp.Width * bmp.Height);

            for (int i = 0; i < bmp.Width; i++)
            {
                for (int j = 0; j < bmp.Height; j++)
                {
                    //獲取該點的像素的RGB的顏色
                    Color color = bmp.GetPixel(i, j);
                    int value = 255 - color.B;
                    Color newColor = value > average ? Color.FromArgb(0, 0, 0): Color.FromArgb(255,

255, 255);                   
                    bmp.SetPixel(i, j, newColor);
                }
            }
            return bmp;
        }

        /// <summary>
        /// 圖像二值化2
        /// </summary>
        /// <param name="img"></param>
        /// <returns></returns>
        public static Bitmap ConvertTo1Bpp2(Bitmap img)
        {
            int w = img.Width;
            int h = img.Height;
            Bitmap bmp = new Bitmap(w, h, PixelFormat.Format1bppIndexed);
            BitmapData data = bmp.LockBits(new Rectangle(0, 0, w, h), ImageLockMode.ReadWrite,

PixelFormat.Format1bppIndexed);
            for (int y = 0; y < h; y++)
            {
                byte[] scan = new byte[(w + 7) / 8];
                for (int x = 0; x < w; x++)
                {
                    Color c = img.GetPixel(x, y);
                    if (c.GetBrightness() >= 0.5) scan[x / 8] |= (byte)(0x80 >> (x % 8));
                }
                Marshal.Copy(scan, 0, (IntPtr)((int)data.Scan0 + data.Stride * y), scan.Length);
            }
            return bmp;
        }