//定義sobel算子函數private static Bitmap sobel(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++)   {    //邊緣八個點像素不變    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, r1, r2, r3, r4, r5, r6, r7, r8;    int g1, g2, g3, g4, g5, g6, g7, g8, g0;    int b1, b2, b3, b4, b5, b6, b7, b8, b0;    double vR, vG, vB;    //左上    p = pIn - stride - 3;    r1 = p[2];    g1 = p[1];    b1 = p[0];    //正上    p = pIn - stride;    r2 = p[2];    g2 = p[1];    b2 = p[0];    //右上    p = pIn - stride + 3;    r3 = p[2];    g3 = p[1];    b3 = p[0];    //左    p = pIn - 3;    r4 = p[2];    g4 = p[1];    b4 = p[0];    //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];    // 右下     p = pIn + stride + 3;    r8 = p[2];    g8 = p[1];    b8 = p[0];    //中心點    p = pIn;    r0 = p[2];    g0 = p[1];    b0 = p[0];    //使用模板    vR = (double)(Math .Abs (r1+2*r4+r6-r3-2*r5-r8)+Math .Abs (r1+2*r2+r3-r6-2*r7-r8));    vG = (double)(Math .Abs (g1+2*g4+g6-g3-2*g5-g8)+Math .Abs (g1+2*g2+g3-g6-2*g7-g8));    vB = (double)(Math .Abs (b1+2*b4+b6-b3-2*b5-b8)+Math .Abs (b1+2*b2+b3-b6-2*b7-b8));    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; }}