Fastest way to convert image to ARGB Array

Question

i want to create an application that delete the duplicated photo in some folder so i need to convert an image to an ARGB array [one diemnsion] then compare them . What is the fastest way to convert an Image to ARGB array? or how to improve this code ?

 Image img;
 using (FileStream stream = new FileStream(imagefile, FileMode.Open))
            {
                img = Image.FromStream(stream);
            }

 using (Bitmap bmp = new Bitmap(img))
            {
                int[] argb = new int[bmp.Width * bmp.Height];
                for (int x = 0; x < bmp.Width; x++)
                {

                    for (int y = 0; y < bmp.Height; y++)
                    {

                        Color pxl = bmp.GetPixel(x, y);

                        argb[x * y] = pxl.ToArgb();



                    }
                }
              }

Answer 1

将图像转换为位图后，所有像素的半透明性值为255 ...