c# - Zhang-Suen细化算法C#

Question

我正在尝试按照此指南在 C# 中编写 Zhang-Suen 细化算法，而不处理边距。

在“zhangsuen”函数中，我正在读取图像“imgUndo”并写入图像“img”。 for 循环中的指针 dataPtrOrigin_aux 用于读取 3x3 窗口内的 9 个像素，使得 dataPtrOrigin_aux5 是该窗口的中心像素，并且该窗口将沿着整个图像移动，从左到右，从上到下移动。在每个像素中，如果if语句被验证为真，则对指针dataPtrFinal要写入的图像进行相应的更改。

请注意，我将当前像素的邻居存储在一个 8 元素数组中。因此，它们将按照以下顺序存储:

        internal static void zhangsuen(Image<Bgr, byte> img, Image<Bgr, byte> imgUndo)
    {
        unsafe
        {

            MIplImage m = img.MIplImage; //Image to be written.
            MIplImage mUndo = imgUndo.MIplImage; //Image to be read.
            byte* dataPtrFinal = (byte*)m.imageData.ToPointer();
            byte* dataPtrUndo = (byte*)mUndo.imageData.ToPointer();

            int width = img.Width; //Width of the image.
            int height = img.Height; //Height of the image.
            int nChan = m.nChannels; //3 channels (R, G, B).
            int wStep = m.widthStep; //Total width of the image (including padding).
            int padding = wStep - nChan * width; //Padding at the end of each line.

            int x, y, i;

            int[] neighbours = new int[8]; //Store the value of the surrounding neighbours in this array.

            int step; //Step 1 or 2.
            int[] sequence = { 1, 2, 4, 7, 6, 5, 3, 0, 1 };
            int blackn = 0; //Number of black neighbours.
            int numtransitions = 0; //Number of transitions from white to black in the sequence specified by the array sequence.
            int changed = 1; //Just so it enters the while.

            bool isblack = false;

            int counter = 0;


            while(changed > 0)
            {
                changed = 0;

                if (counter % 2 == 0) //We want to read all the pixels in the image before going to the next step
                    step = 1;
                else
                    step = 2;

                for (y = 0; y < height; y++)
                {
                    for (x = 0; x < width; x++)
                    {

                            byte* dataPtrOrigin_aux1 = (byte*)(dataPtrUndo + (y - 1) * m.widthStep + (x - 1) * m.nChannels);
                            byte* dataPtrOrigin_aux2 = (byte*)(dataPtrUndo + (y - 1) * m.widthStep + (x) * m.nChannels);
                            byte* dataPtrOrigin_aux3 = (byte*)(dataPtrUndo + (y - 1) * m.widthStep + (x + 1) * m.nChannels);
                            byte* dataPtrOrigin_aux4 = (byte*)(dataPtrUndo + (y) * m.widthStep + (x - 1) * m.nChannels);
                            byte* dataPtrOrigin_aux5 = (byte*)(dataPtrUndo + (y) * m.widthStep + (x) * m.nChannels);
                            byte* dataPtrOrigin_aux6 = (byte*)(dataPtrUndo + (y) * m.widthStep + (x + 1) * m.nChannels);
                            byte* dataPtrOrigin_aux7 = (byte*)(dataPtrUndo + (y + 1) * m.widthStep + (x - 1) * m.nChannels);
                            byte* dataPtrOrigin_aux8 = (byte*)(dataPtrUndo + (y + 1) * m.widthStep + (x) * m.nChannels);
                            byte* dataPtrOrigin_aux9 = (byte*)(dataPtrUndo + (y + 1) * m.widthStep + (x + 1) * m.nChannels);


                        if (x > 0 && y > 0 && x < width - 1 && y < height - 1)
                        {
                            if (dataPtrOrigin_aux5[0] == 0)
                                isblack = true;

                            if (isblack)
                            {

                                neighbours[0] = dataPtrOrigin_aux1[0];
                                neighbours[1] = dataPtrOrigin_aux2[0];
                                neighbours[2] = dataPtrOrigin_aux3[0];
                                neighbours[3] = dataPtrOrigin_aux4[0];
                                neighbours[4] = dataPtrOrigin_aux6[0];
                                neighbours[5] = dataPtrOrigin_aux7[0];
                                neighbours[6] = dataPtrOrigin_aux8[0];
                                neighbours[7] = dataPtrOrigin_aux9[0];

                                for(i = 0; i <= 7; i++)
                                {
                                    if (neighbours[i] == 0)
                                        blackn++;

                                    if (neighbours[sequence[i]] - neighbours[sequence[i + 1]] == 255) //número de transições de branco para preto, seguindo a ordem do vector sequence
                                        numtransitions++;
                                }


                                if ((blackn >= 2 && blackn <= 6) && numtransitions == 1)
                                {
                                        if (step == 1 && (neighbours[1] == 255 || neighbours[4] == 255 || neighbours[6] == 255) && (neighbours[4] == 255 || neighbours[6] == 255 || neighbours[3] == 255))
                                        {
                                            dataPtrFinal[0] = 255;
                                            dataPtrFinal[1] = 255;
                                            dataPtrFinal[2] = 255;

                                            changed++;
                                        }

                                        if (step == 2 && (neighbours[1] == 255 || neighbours[4] == 255 || neighbours[3] == 255) && (neighbours[1] == 255 || neighbours[6] == 255 || neighbours[3] == 255))
                                        {
                                            dataPtrFinal[0] = 255;
                                            dataPtrFinal[1] = 255;
                                            dataPtrFinal[2] = 255;

                                            changed++;
                                        }

                                }
                            }
                        }


                        dataPtrFinal += nChan;

                        isblack = false;
                        blackn = 0;
                        numtransitions = 0;

                    }
                    dataPtrFinal += padding;

                }


                dataPtrUndo = (byte*)m.imageData.ToPointer(); //Change the image to be read to the one that has just been written.

                counter++;

            }


        }
    }

当我结束读取第一张图像并将更改写入图像“img”时(一旦 (y = 0; y < height; y++) 的循环结束，我希望我刚刚写入的图像成为我将在下一个周期中阅读，以便进一步细化。我试图用这条线来完成这一点

dataPtrUndo = (byte*)m.imageData.ToPointer();

虽然计数器的某个值大于 0(取决于读取的图像)，但我收到一条错误消息，指出已尝试写入 protected 内存，这表明我已尝试在图像限制之外写入，但我不明白为什么。它是我错误地做的最后归因于 dataPtrUndo 吗？

Answer 1

这是我对 Zhang-Suen 细化算法的 C# 实现

public static bool[][] ZhangSuenThinning(bool[][] s)
    {
        bool[][] temp = s;
        bool even = true;

        for (int a = 1; a < s.Length-1; a++)
        {
            for (int b = 1; b < s[0].Length-1; b++)
            {
                if (SuenThinningAlg(a, b, temp, even))
                {
                    temp[a][b] = false;
                }
                even = !even;
            }
        }

        return temp;
    }
static bool SuenThinningAlg(int x, int y, bool[][] s, bool even)
    {
        bool p2 = s[x][y - 1];
        bool p3 = s[x + 1][y - 1];
        bool p4 = s[x + 1][y];
        bool p5 = s[x + 1][y + 1];
        bool p6 = s[x][y + 1];
        bool p7 = s[x - 1][y + 1];
        bool p8 = s[x - 1][y];
        bool p9 = s[x - 1][y - 1];


            int bp1 = NumberOfNonZeroNeighbors(x, y, s);
            if (bp1 >= 2 && bp1 <= 6)//2nd condition
            {
                if (NumberOfZeroToOneTransitionFromP9(x, y, s) == 1)
                {
                    if (even)
                    {
                        if (!((p2 && p4) && p8))
                        {
                            if (!((p2 && p6) && p8))
                            {
                                return true;
                            }
                        }
                    }
                    else
                    {
                        if (!((p2 && p4) && p6))
                        {
                            if (!((p4 && p6) && p8))
                            {
                                return true;
                            }
                        }
                    }
                }
            }


        return false;
    }
    static int NumberOfZeroToOneTransitionFromP9(int x, int y, bool[][]s)
    {
        bool p2 = s[x][y - 1];
        bool p3 = s[x + 1][y - 1];
        bool p4 = s[x + 1][y];
        bool p5 = s[x + 1][y + 1];
        bool p6 = s[x][y + 1];
        bool p7 = s[x - 1][y + 1];
        bool p8 = s[x - 1][y];
        bool p9 = s[x - 1][y - 1];

        int A = Convert.ToInt32((p2 == false && p3 == true)) + Convert.ToInt32((p3 == false && p4 == true)) +
                 Convert.ToInt32((p4 == false && p5 == true)) + Convert.ToInt32((p5 == false && p6 == true)) +
                 Convert.ToInt32((p6 == false && p7 == true)) + Convert.ToInt32((p7 == false && p8 == true)) +
                 Convert.ToInt32((p8 == false && p9 == true)) + Convert.ToInt32((p9 == false && p2 == true));
        return A;
    }
    static int NumberOfNonZeroNeighbors(int x, int y, bool[][]s)
    {
        int count = 0;
        if (s[x-1][y])
            count++;
        if (s[x-1][y+1])
            count++;
        if (s[x-1][y-1])
            count++;
        if (s[x][y+1])
            count++;
        if (s[x][y-1])
            count++;
        if (s[x+1][y])
            count++;
        if (s[x+1][y+1])
            count++;
        if (s[x+1][y-1])
            count++;
        return count;
    }