柔化效果

 Bitmap bmp = new Bitmap(pictureBox1.Image);
            int Height = bmp.Height;
            int Width = bmp.Width;
            Bitmap tmp = (Bitmap)bmp.Clone();

            Color pixel;
            //高斯模板
            int[] Gauss = { 1, 2, 1, 2, 4, 2, 1, 2, 1 };
            for (int x = 1; x < Width - 1; x++)
                for (int y = 1; y < Height - 1; y++)
                {
                    int r = 0, g = 0, b = 0;
                    int Index = 0;
                    for (int col = -1; col <= 1; col++)
                        for (int row = -1; row <= 1; row++)
                        {
                            pixel = bmp.GetPixel(x + row, y + col);
                            r += pixel.R * Gauss[Index];
                            g += pixel.G * Gauss[Index];
                            b += pixel.B * Gauss[Index];
                            Index++;
                        }
                    r /= 16;
                    g /= 16;
                    b /= 16;
                    //处理颜色值溢出
                    r = r > 255 ? 255 : r;
                    r = r < 0 ? 0 : r;
                    g = g > 255 ? 255 : g;
                    g = g < 0 ? 0 : g;
                    b = b > 255 ? 255 : b;
                    b = b < 0 ? 0 : b;
                    tmp.SetPixel(x - 1, y - 1, Color.FromArgb(r, g, b));
                }
            this.pictureBox2.Image = tmp;