Accessing a bitmap with pointers

BitmapData bData = m_Imgs[i].LockBits(new Rectangle(0, 0, Width, Height), System.Drawing.Imaging.ImageLockMode.ReadOnly, System.Drawing.Imaging.PixelFormat.Format32bppRgb);
int[] imageData = new int[m_Imgs[i].Width * m_Imgs[i].Height];
                                
Marshal.Copy(bData.Scan0, imageData, 0, imageData.Length);
for (int x = 0; x < imageData.Length; x++)
    {
    imageData[x] = 255 - imageData[x]; 
    }

   Marshal.Copy(imageData, 0, bData.Scan0, imageData.Length);
   // Unlock it kill it resize it!
    m_Imgs[i].UnlockBits(bData);
    m_Imgs[i].Dispose();
    m_Imgs[i] = new Bitmap(Width, Height, System.Drawing.Imaging.PixelFormat.Format32bppRgb);
   m_PicBoxes[i].Image = m_Imgs[i];