[函数名称]

  二值图像细化算法      WriteableBitmap ThinningProcess(WriteableBitmap src)

[算法说明]

  图像细化（Image Thinning），一般指二值图像的骨架化（Image Skeletonization）的一种操作运算。

所谓的细化就是经过一层层的剥离，从原来的图中去掉一些点，但仍要保持原来的形状，直到得到图

像的骨架。骨架，可以理解为图象的中轴。

  细化算法有很多，我们这里介绍一种二值图像的快速细化算法—Zhang 细化算法，该算法是Zhang于

1984年提出。

  算法过程如下：

  1，设二值图像中0为背景，1为目标。目标像素的8邻域如下图所示：

        /// <summary>
        /// Zhang's fast thinning process for binary image.
        /// </summary>
        /// <param name="src">The source image.</param>
        /// <returns></returns>
        public static WriteableBitmap ThinningProcess(WriteableBitmap src)////二值图像细化(Zhang快速细化算法)
        {
            if (src != null)
            {
                int w = src.PixelWidth;
                int h = src.PixelHeight;
                WriteableBitmap srcImage = new WriteableBitmap(w, h);
                byte[] temp = src.PixelBuffer.ToArray();
                byte[] tempMask = (byte[])temp.Clone();
                int[,] srcBytes = new int[w, h];
                for (int j = 0; j < h; j++)
                {
                    for (int i = 0; i < w ; i++)
                    {
                        srcBytes[i, j] = (tempMask[i * 4 + j * w * 4] * 0.114 + tempMask[i * 4 + 1 + j * w * 4] * 0.587 + tempMask[i * 4 + 2 + j * w * 4] * 0.299 < 128 ? 0 : 1);
                    }
                }
                Thinning(ref srcBytes, w, h);
                for (int j = 0; j < h; j++)
                {
                    for (int i = 0; i < w; i++)
                    {
                        temp[i * 4 + j * w * 4] = temp[i * 4 + 1 + j * w * 4] = temp[i * 4 + 2 + j * w * 4] = (byte)(srcBytes[i, j] * 255);
                    }
                }
                Stream sTemp = srcImage.PixelBuffer.AsStream();
                sTemp.Seek(0, SeekOrigin.Begin);
                sTemp.Write(temp, 0, w * 4 * h);
                return srcImage;
            }
            else
            {
                return null;
            }
        }
        private static void Thinning(ref int[,] srcBytes,int w,int h)
        {
            int[] srcTemp;
            int countNumber;
            do
            {
                countNumber = 0;
                for (int y = 1; y < h - 1; y++)
                {
                    for (int x = 1; x < w - 1; x++)
                    {
                        srcTemp = new int[9] { srcBytes[x, y], srcBytes[x - 1, y - 1], srcBytes[x, y - 1], srcBytes[x + 1, y - 1], srcBytes[x + 1, y], srcBytes[x + 1, y + 1], srcBytes[x, y + 1], srcBytes[x - 1, y + 1], srcBytes[x - 1, y] };
                        if (srcBytes[x, y] != 1)
                        {
                            if (CountN(srcTemp) >= 2 && CountN(srcTemp) <= 6)
                            {
                                if (CountT(srcTemp) == 1)
                                {
                                    if (srcBytes[x, y - 1] * srcBytes[x + 1, y] * srcBytes[x, y + 1] == 0)
                                    {
                                        if (srcBytes[x - 1, y] * srcBytes[x + 1, y] * srcBytes[x, y + 1] == 0)
                                        {
                                            srcBytes[x, y] = (byte)1;
                                            countNumber++;
                                        }
                                    }
                                    else
                                    {
                                        if (srcBytes[x, y - 1] * srcBytes[x + 1, y] * srcBytes[x - 1, y] == 0)
                                        {
                                            if (srcBytes[x, y - 1] * srcBytes[x, y + 1] * srcBytes[x - 1, y] == 0)
                                            {
                                                srcBytes[x, y] = (byte)1;
                                                countNumber++;
                                            }
                                        }
                                    }
                                }
                            }
                        }
                    }
                }
            } while (countNumber != 0);
        }
        private static int CountN(params int[] src)
        {
            int count = 0;
            for (int i = 0; i < src.Length; i++)
            {
                if (src[i] == 0)
                {
                    count++;
                }
            }
            return count;
        }
        private static int CountT(params int[] src)
        {
            int count = 0;
            for (int i = 1; i < src.Length; i++)
            {
                if (src[i] == 1 && src[i - 1] == 0)
                {
                    count++;
                }
            }
            if (src[src.Length - 1] == 0 && src[0] == 1)
            {
                count++;
            }
            return count;
        }