C#图像边缘检测（Roberts）的方法

//定义roberts算子函数private static Bitmap robert(Bitmap a){ int w = a.Width; int h = a.Height; try {  Bitmap dstBitmap = new Bitmap(w, h, System.Drawing.Imaging.PixelFormat.Format24bppRgb);  System.Drawing.Imaging.BitmapData srcData = a.LockBits(new Rectangle   (0, 0, w, h), System.Drawing.Imaging.ImageLockMode.ReadOnly, System.Drawing.Imaging.PixelFormat.Format24bppRgb);  System.Drawing.Imaging.BitmapData dstData = dstBitmap.LockBits(new Rectangle   (0, 0, w, h), System.Drawing.Imaging.ImageLockMode.WriteOnly, System.Drawing.Imaging.PixelFormat.Format24bppRgb);  unsafe  {   byte* pIn = (byte*)srcData.Scan0.ToPointer();   byte* pOut = (byte*)dstData.Scan0.ToPointer();   byte* p;   int stride = srcData.Stride;   for (int y = 0; y < h; y++)   {   for (int x = 0; x < w; x++)   {    //边缘八个点像素不变    if (x == 0 || x == w - 1 || y == 0 || y == h - 1)    {    pOut[0] = pIn[0];    pOut[1] = pIn[1];    pOut[2] = pIn[2];    }    else    {    int r0, r5, r6, r7;    int g5, g6, g7, g0;    int b5, b6, b7, b0;    double vR, vG, vB;    //右    p = pIn + 3;    r5 = p[2];    g5 = p[1];    b5 = p[0];    //左下    p = pIn + stride - 3;    r6 = p[2];    g6 = p[1];    b6 = p[0];    //正下    p = pIn + stride;    r7 = p[2];    g7 = p[1];    b7 = p[0];    //中心点    p = pIn;    r0 = p[2];    g0 = p[1];    b0 = p[0];    vR = (double)(Math .Abs (r0-r5)+Math .Abs ( r5-r7));    vG = (double)(Math.Abs(g0 - g5) + Math.Abs(g5 - g7));    vB = (double)(Math.Abs(b0 - b5) + Math.Abs(b5 - b7));    if (vR > 0)    {     vR = Math.Min(255, vR);    }    else    {     vR = Math.Max(0, vR);    }    if (vG > 0)    {     vG = Math.Min(255, vG);    }    else    {     vG = Math.Max(0, vG);    }    if (vB > 0)    {     vB = Math.Min(255, vB);    }    else    {     vB = Math.Max(0, vB);    }    pOut[0] = (byte)vB;    pOut[1] = (byte)vG;    pOut[2] = (byte)vR;    }    pIn += 3;    pOut += 3;   }   pIn += srcData.Stride - w * 3;   pOut += srcData.Stride - w * 3;   }  }  a.UnlockBits(srcData);  dstBitmap.UnlockBits(dstData);  return dstBitmap; } catch {  return null; }}