AForge.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 P5 PGM image (grayscale PNM image with binary encoding)
        private static unsafe Bitmap ReadP5Image(Stream stream, int width, int height, int maxValue)
        {
            var scalingFactor = (double)255 / maxValue;

            // create new bitmap and lock it
            var image     = Tools.CreateGrayscaleImage(width, height);
            var imageData = image.LockBits(new Rectangle(0, 0, width, height),
                                           ImageLockMode.ReadWrite, PixelFormat.Format8bppIndexed);

            var stride = imageData.Stride;
            var ptr    = (byte *)imageData.Scan0.ToPointer();

            // prepare a buffer for one line
            var line = new byte[width];

            int totalBytesRead = 0, bytesRead = 0;

            // load all rows
            for (var y = 0; y < height; y++)
            {
                totalBytesRead = 0;
                bytesRead      = 0;

                // load next line
                while (totalBytesRead != width)
                {
                    bytesRead = stream.Read(line, totalBytesRead, width - totalBytesRead);

                    if (bytesRead == 0)
                    {
                        // if we've reached the end before complete image is loaded, then there should
                        // be something wrong
                        throw new Exception();
                    }

                    totalBytesRead += bytesRead;
                }

                // fill next image row
                var row = ptr + stride * y;

                for (var x = 0; x < width; x++, row++)
                {
                    *row = (byte)(scalingFactor * line[x]);
                }
            }

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