private void CmdFragment_Click(object sender, EventArgs e)
{int X, Y, Z, XX, YY;int Width, Height, Stride;int Speed, Index;int SumR, SumG, SumB;Bitmap Bmp = (Bitmap)Pic.Image;if (Bmp.PixelFormat != PixelFormat.Format24bppRgb) throw new Exception("不支持的图像格式.");Width = Bmp.Width; Height = Bmp.Height; Stride = (int)((Bmp.Width * 3 + 3) & 0XFFFFFFFC);byte[] ImageData = new byte[Stride * Height];                                    // 用于保存图像数据，（处理前后的都为他)byte[] ImageDataC = new byte[Stride * Height];                                   // 用于保存克隆的图像数据int[] OffsetX = new int[] { 4, -4, -4, 4 };                                      // 每个点的偏移量int[] OffsetY = new int[] { -4, -4, 4, 4 };fixed (byte* P = &ImageData[0], CP = &ImageDataC[0]){byte* DataP = P, DataCP = CP;BitmapData BmpData = new BitmapData();BmpData.Scan0 = (IntPtr)DataP;                                              //  设置为字节数组的的第一个元素在内存中的地址BmpData.Stride = Stride;Bmp.LockBits(new Rectangle(0, 0, Bmp.Width, Bmp.Height), ImageLockMode.ReadWrite | ImageLockMode.UserInputBuffer, PixelFormat.Format24bppRgb, BmpData);Stopwatch Sw = new Stopwatch();                                             //  只获取计算用时Sw.Start();System.Buffer.BlockCopy(ImageData, 0, ImageDataC, 0, Stride * Height);     //  填充克隆数据        for (Y = 0; Y < Height; Y++){Speed = Y * Stride;for (X = 0; X < Width; X++){SumB = 0; SumG = 0; SumR = 0;for (Z = 0; Z < 4; Z++)                                           //  累积取样点的取样和{XX = X + OffsetX[Z];YY = Y + OffsetY[Z];if (XX < 0)                                                    //   注意越界XX = 0;else if (XX >= Width)XX = Width - 1;if (YY < 0)YY = 0;else if (YY >= Height)YY = Height - 1;Index = YY * Stride + XX * 3;SumB += DataCP[Index];SumG += DataCP[Index + 1];SumR += DataCP[Index + 2];}DataP[Speed] = (byte)((SumB+2) >> 2);    //  求平均值(Sum+2)/4,为什么要+2，就为了四舍五入。比如如果计算结果为108.6，则取像素109更为合理     DataP[Speed + 1] = (byte)((SumG + 2) >> 2);DataP[Speed + 2] = (byte)((SumR + 2) >> 2);Speed += 3;                                                     //  跳往下一个像素}}Sw.Stop();this.Text = "计算用时: " + Sw.ElapsedMilliseconds.ToString() + " ms";Bmp.UnlockBits(BmpData);                         //  必须先解锁，否则Invalidate失败 }Pic.Invalidate();
}

while (XX >= Width)XX = XX - Width;
while (XX < 0)XX = XX + Width;
while (YY >= Height)YY = YY - Height;
while (YY < 0)YY = YY + Height;

 if (XX >= 0 && XX < Width && YY >= 0 && YY < Height){// 累加计算}