改進Zhang Suen細化算法的C#實現

本文主要實現了改進Zhang Suen細化算法的C#實現，相關論文 ：“牟少敏,杜海洋,蘇平,查緒恆,陳光藝.一種改進的快速並行細化算法[J].微電子學與計算機,2013,(第1期)” 。這篇論文中關於Zhang Suen細化算法的描述，貌似存在問題。本文的算法中的意思是兩次標記的點迭代后同時刪除。而zhang快速算法，是分為兩步刪除邊界點的。第一步迭代之后，已經做標記的點就需要刪除了。如果兩步可以放在一起刪除的話，為什么不在一次迭代中將幾個條件一起判斷呢

一：Zhang-Suen細化算法介紹

Zhang-Suen細化算法通常是一個迭代算法，整個迭代過程分為兩步：

Step One：循環所有前景像素點，對符合如下條件的像素點標記為刪除：

1.      2 <= N(p1) <=6

2.      S(P1) = 1

3.      P2 * P4 * P6 = 0

4.      P4 * P6 * P8 = 0

其中N(p1)表示跟P1相鄰的8個像素點中，為前景像素點的個數

S(P1)表示從P2 ～ P9 ～ P2像素中出現0～1的累計次數，其中0表示背景，1表示前景

完整的P1 ～P9的像素位置與舉例如下：

 

其中 N(p1) = 4, S(P1) = 3, P2*P4*P6=0*0*0=0, P4*P6*P8=0*0*1=0, 不符合條件，無需標記為刪除。

Step Two：跟Step One很類似，條件1、2完全一致，只是條件3、4稍微不同，滿足如下條件的像素P1則標記為刪除，條件如下：

1.      2 <= N(p1) <=6

2.      S(P1) = 1

3.      P2 * P4 * P8 = 0

4.      P2 * P6 * P8 = 0

循環上述兩步驟，直到兩步中都沒有像素被標記為刪除為止，輸出的結果即為二值圖像細化后的骨架。

 

二：代碼實現步驟

        #region 改進 Zhang-Suen algorithm

        public Bitmap zhang_thinimage_improve(Bitmap bmp)
        {
            int imgWidth = bmp.Width;
            int imgHeight = bmp.Height;
            byte[,] BinaryArray = new byte[imgHeight, imgWidth];
            int depth = Bitmap.GetPixelFormatSize(bmp.PixelFormat);
            if (depth != 1)//判斷位深度 
            {
                int threshold = 0;
                BinaryArray = ToBinaryArray(bmp, out threshold);
            }
            else
            {
                BinaryArray = BinaryBitmapToBinaryArray(bmp);
            }
            int[] Zhangmude = new int[9];
            //int deletecount = 0;
            List<Point> deletelist = new List<Point>();
            while (true)
            {
                for (int y = 1; y < imgHeight-1; y++)
                {
                    for (int x = 1; x < imgWidth-2; x++)
                    {
                        if (BinaryArray[y, x] == 0)
                        {
                            Zhangmude[0] = 1;
                            if (BinaryArray[y - 1, x] == 0) Zhangmude[1] = 1;
                            else Zhangmude[1] = 0;
                            if (BinaryArray[y - 1, x + 1] == 0) Zhangmude[2] = 1;
                            else Zhangmude[2] = 0;
                            if (BinaryArray[y, x + 1] == 0) Zhangmude[3] = 1;
                            else Zhangmude[3] = 0;
                            if (BinaryArray[y + 1, x + 1] == 0) Zhangmude[4] = 1;
                            else Zhangmude[4] = 0;
                            if (BinaryArray[y + 1, x] == 0) Zhangmude[5] = 1;
                            else Zhangmude[5] = 0;
                            if (BinaryArray[y + 1, x - 1] == 0) Zhangmude[6] = 1;
                            else Zhangmude[6] = 0;
                            if (BinaryArray[y, x - 1] == 0) Zhangmude[7] = 1;
                            else Zhangmude[7] = 0;
                            if (BinaryArray[y - 1, x - 1] == 0) Zhangmude[8] = 1;
                            else Zhangmude[8] = 0;
                            int whitepointtotal = 0;
                            for (int k = 1; k < 9; k++)
                            {
                                //得到1的個數
                                whitepointtotal = whitepointtotal + Zhangmude[k];
                            }
                            if ((whitepointtotal >= 2) && (whitepointtotal <= 6))
                            {
                                //得到01的個數
                                int ap = 0;
                                if ((Zhangmude[1] == 0) && (Zhangmude[2] == 1)) ap++;
                                if ((Zhangmude[2] == 0) && (Zhangmude[3] == 1)) ap++;
                                if ((Zhangmude[3] == 0) && (Zhangmude[4] == 1)) ap++;
                                if ((Zhangmude[4] == 0) && (Zhangmude[5] == 1)) ap++;
                                if ((Zhangmude[5] == 0) && (Zhangmude[6] == 1)) ap++;
                                if ((Zhangmude[6] == 0) && (Zhangmude[7] == 1)) ap++;
                                if ((Zhangmude[7] == 0) && (Zhangmude[8] == 1)) ap++;
                                if ((Zhangmude[8] == 0) && (Zhangmude[1] == 1)) ap++;
                                //計算bp
                                int bp = 0;
                                bp += Zhangmude[1];
                                bp += Zhangmude[2] << 1;
                                bp += Zhangmude[3] << 2;
                                bp += Zhangmude[4] << 3;
                                bp += Zhangmude[5] << 4;
                                bp += Zhangmude[6] << 5;
                                bp += Zhangmude[7] << 6;
                                bp += Zhangmude[8] << 7;
                                if (ap == 1 || bp == 65 || bp == 5 || bp == 20 || bp == 80 || bp == 13 || bp == 22 || bp == 52 || bp == 133 || bp == 141 || bp == 54)
                                {
                                    if ((Zhangmude[1] * Zhangmude[3] * Zhangmude[5] == 0) && (Zhangmude[3] * Zhangmude[5] * Zhangmude[7] == 0))
                                    {
                                        deletelist.Add(new Point(y, x));
                                    }
                                }
                            }
                        }
                    }
                }
                if (deletelist.Count() == 0) break;
                foreach (var deleteItem in deletelist)
                {
                    BinaryArray[deleteItem.X, deleteItem.Y] = 255;
                }
                deletelist.Clear();
                for (int y = 1; y < imgHeight-1; y++)
                {
                    for (int x = 1; x < imgWidth-1; x++)
                    {
                        if (BinaryArray[y, x] == 0)
                        {
                            Zhangmude[0] = 1;
                            if (BinaryArray[y - 1, x] == 0) Zhangmude[1] = 1;
                            else Zhangmude[1] = 0;
                            if (BinaryArray[y - 1, x + 1] == 0) Zhangmude[2] = 1;
                            else Zhangmude[2] = 0;
                            if (BinaryArray[y, x + 1] == 0) Zhangmude[3] = 1;
                            else Zhangmude[3] = 0;
                            if (BinaryArray[y + 1, x + 1] == 0) Zhangmude[4] = 1;
                            else Zhangmude[4] = 0;
                            if (BinaryArray[y + 1, x] == 0) Zhangmude[5] = 1;
                            else Zhangmude[5] = 0;
                            if (BinaryArray[y + 1, x - 1] == 0) Zhangmude[6] = 1;
                            else Zhangmude[6] = 0;
                            if (BinaryArray[y, x - 1] == 0) Zhangmude[7] = 1;
                            else Zhangmude[7] = 0;
                            if (BinaryArray[y - 1, x - 1] == 0) Zhangmude[8] = 1;
                            else Zhangmude[8] = 0;
                            int whitepointtotal = 0;
                            for (int k = 1; k < 9; k++)
                            {
                                //得到1的個數
                                whitepointtotal = whitepointtotal + Zhangmude[k];
                            }
                            if ((whitepointtotal >= 2) && (whitepointtotal <= 6))
                            {
                                //得到01的個數
                                int ap = 0;
                                if ((Zhangmude[1] == 0) && (Zhangmude[2] == 1)) ap++;
                                if ((Zhangmude[2] == 0) && (Zhangmude[3] == 1)) ap++;
                                if ((Zhangmude[3] == 0) && (Zhangmude[4] == 1)) ap++;
                                if ((Zhangmude[4] == 0) && (Zhangmude[5] == 1)) ap++;
                                if ((Zhangmude[5] == 0) && (Zhangmude[6] == 1)) ap++;
                                if ((Zhangmude[6] == 0) && (Zhangmude[7] == 1)) ap++;
                                if ((Zhangmude[7] == 0) && (Zhangmude[8] == 1)) ap++;
                                if ((Zhangmude[8] == 0) && (Zhangmude[1] == 1)) ap++;
                                //計算bp
                                int bp = 0;
                                bp += Zhangmude[1];
                                bp += Zhangmude[2] << 1;
                                bp += Zhangmude[3] << 2;
                                bp += Zhangmude[4] << 3;
                                bp += Zhangmude[5] << 4;
                                bp += Zhangmude[6] << 5;
                                bp += Zhangmude[7] << 6;
                                bp += Zhangmude[8] << 7;
                                if (ap == 1 || bp == 65 || bp == 5 || bp == 20 || bp == 80 || bp == 13 || bp == 22 || bp == 52 || bp == 133 || bp == 141 || bp == 54)
                                {
                                    if ((Zhangmude[1] * Zhangmude[3] * Zhangmude[7] == 0) && (Zhangmude[1] * Zhangmude[5] * Zhangmude[7] == 0))
                                    {
                                        deletelist.Add(new Point(y, x));
                                    }
                                }
                            }
                        }
                    }
                }
                if (deletelist.Count() == 0) break;
                foreach (var deleteItem in deletelist)
                {
                    BinaryArray[deleteItem.X, deleteItem.Y] = 255;
                }
                deletelist.Clear();
            }
            Bitmap dstBmp = BinaryArrayToBinaryBitmap(BinaryArray);
            return dstBmp;

        }

        #endregion

 

還有一個問題需要注意，找到要刪除的點之后不能立即刪除，而是把找到的點做標記，等第一步全部遍歷完之后才刪除標記的點。同樣第二步也是這樣。

 

下面是實驗結果：

  

 

 

本文借鑒了兩篇博客，下面是原文地址：

https://blog.csdn.net/u011941438/article/details/54628836

https://blog.csdn.net/jia20003/article/details/52142992