C# 图像处理浮雕效果问题

Question

像素点的像素值与相邻像素点的像素值相减后加上128, 然后将其作为新的像素点的值.
注意:
此时For循环的时候，x<oldPic.Width -1即可，y同样。
判断，若r、g、b的值<0，则设置=0，若>255，则设置=255; private void tsbtnFudiao_Click(object sender, EventArgs e)
        {
                       Color oldNeiColor;
            for (int x = 1; x < oldpic.Width-1; x++)
            {
                for (int y = 1; y < oldpic.Height-1; y++)
                {
                    oldlColor = oldpic.GetPixel(x, y);
                    oldNeiColor = oldpic.GetPixel(x + 1, y + 1);
                    int r = oldlColor.R - oldNeiColor.R + 128;
                    int g = oldlColor.G - oldNeiColor.G + 128;
                    int b = oldlColor.B - oldNeiColor.B + 128;
                    int[] arr = { r, g, b };
                    for (int i = 0; i < arr.Length; i++)
                    {
                        
                        if (arr[i] < 0)
                        {
                            arr[i] = 0;
                          
                        }
                         else if (arr[i] > 255)
                        {
                            arr[i] = 255;
                         
                        }
                    
                         
                    }
                    newColor = Color.FromArgb(r, g, b);
                    newpic.SetPixel(x, y, newColor);
                }
                progressBar1.Maximum = newpic.Width;
                progressBar1.Value = x;
                this.Refresh();
                picShow.Image = newpic;
            }

                  int[] arr = { r, g, b };
                    for (int i = 0; i < arr.Length; i++)
                    {
                        
                        if (arr[i] < 0)
                        {
                            arr[i] = 0;
                          
                        }
                         else if (arr[i] > 255)
                        {
                            arr[i] = 255;
                         
                        }
                    
                         
                    }这里有什么问题，为什么还是有情况就是r，b，g都取到负数和大于255的数

Answer 1

是这里有问题
 newColor = Color.FromArgb(r, g, b); 
newpic.SetPixel(x, y, newColor); 改为：
 newColor = Color.FromArgb(arr[0], arr[1], arr[2]); 
newpic.SetPixel(x, y, newColor);