Accord.Imaging.Formats.Tools.CreateGrayscaleImage C# (CSharp) Method

        public static Bitmap CreateGrayscaleImage( int width, int height )
        {
            // create new image
            Bitmap image = new Bitmap( width, height, PixelFormat.Format8bppIndexed );
            // get palette
            ColorPalette cp = image.Palette;
            // init palette with grayscale colors
            for ( int i = 0; i < 256; i++ )
            {
                cp.Entries[i] = Color.FromArgb( i, i, i );
            }
            // set palette back
            image.Palette = cp;
            // return new image
            return image;
        }

        // Load P2 PGM image (grayscale PNM image with ascii encoding)
        private static unsafe Bitmap ReadP2Image(TextReader stream, int width, int height, int maxValue)
        {
            double scalingFactor = 255 / (double)maxValue;

            // create new bitmap and lock it
            Bitmap     image     = Tools.CreateGrayscaleImage(width, height);
            BitmapData imageData = image.LockBits(ImageLockMode.WriteOnly);

            int   stride = imageData.Stride;
            byte *ptr    = (byte *)imageData.Scan0.ToPointer();
            int   offset = imageData.Stride - imageData.Width;

            // load all rows
            string all = stream.ReadToEnd();

            string[] values = all.Split(emptyChars, StringSplitOptions.RemoveEmptyEntries);

            for (int y = 0, z = 0; y < height; y++)
            {
                // fill next image row
                for (int x = 0; x < width; x++, ptr++, z++)
                {
                    *ptr = (byte)(scalingFactor * Byte.Parse(values[z]));
                }
                ptr += offset;
            }

            // unlock image and return it
            image.UnlockBits(imageData);
            return(image);
        }