Accord.Imaging.Filters.CanvasMove.ProcessFilter8bpc C# (CSharp) Method

        private unsafe void ProcessFilter8bpc(UnmanagedImage image)
        {
            int pixelSize = Image.GetPixelFormatSize(image.PixelFormat) / 8;
            bool is32bpp = (pixelSize == 4);

            // get image width and height
            int width = image.Width;
            int height = image.Height;
            int stride = image.Stride;

            int movePointX = movePoint.X;
            int movePointY = movePoint.Y;

            // intersection rectangle
            Rectangle intersect = Rectangle.Intersect(
                new Rectangle(0, 0, width, height),
                new Rectangle(movePointX, movePointY, width, height));

            // start, stop and step for X adn Y
            int yStart = 0;
            int yStop = height;
            int yStep = 1;
            int xStart = 0;
            int xStop = width;
            int xStep = 1;

            if (movePointY > 0)
            {
                yStart = height - 1;
                yStop = -1;
                yStep = -1;
            }
            if (movePointX > 0)
            {
                xStart = width - 1;
                xStop = -1;
                xStep = -1;
            }

            // do the job
            byte* src = (byte*)image.ImageData.ToPointer();
            byte* pixel, moved;

            if (image.PixelFormat == PixelFormat.Format8bppIndexed)
            {
                // grayscale image
                for (int y = yStart; y != yStop; y += yStep)
                {
                    for (int x = xStart; x != xStop; x += xStep)
                    {
                        // current pixel
                        pixel = src + y * stride + x;

                        if (intersect.Contains(x, y))
                        {
                            moved = src + (y - movePointY) * stride + (x - movePointX);

                            *pixel = *moved;
                        }
                        else
                        {
                            *pixel = fillGray;
                        }
                    }
                }
            }
            else
            {
                // color image
                for (int y = yStart; y != yStop; y += yStep)
                {
                    for (int x = xStart; x != xStop; x += xStep)
                    {
                        // current pixel
                        pixel = src + y * stride + x * pixelSize;

                        if (intersect.Contains(x, y))
                        {
                            moved = src + (y - movePointY) * stride + (x - movePointX) * pixelSize;

                            pixel[RGB.R] = moved[RGB.R];
                            pixel[RGB.G] = moved[RGB.G];
                            pixel[RGB.B] = moved[RGB.B];

                            if (is32bpp)
                            {
                                pixel[RGB.A] = moved[RGB.A];
                            }
                        }
                        else
                        {
                            pixel[RGB.R] = fillRed;
                            pixel[RGB.G] = fillGreen;
                            pixel[RGB.B] = fillBlue;

                            if (is32bpp)
                            {
                                pixel[RGB.A] = fillAlpha;
                            }
                        }
                    }
                }
            }
        }