BmpBitmapDecoder Class

// Open a Uri and decode a BMP image
Uri myUri = new Uri("tulipfarm.bmp", UriKind.RelativeOrAbsolute);
BmpBitmapDecoder decoder2 = new BmpBitmapDecoder(myUri, BitmapCreateOptions.PreservePixelFormat, BitmapCacheOption.Default);
BitmapSource bitmapSource2 = decoder2.Frames[0];

// Draw the Image
Image myImage2 = new Image();
myImage2.Source = bitmapSource2;
myImage2.Stretch = Stretch.None;
myImage2.Margin = new Thickness(20);

            int width = 128;
            int height = width;
            int stride = width / 8;
            byte[] pixels = new byte[height * stride];

            // Try creating a new image with a custom palette.
            List<System.Windows.Media.Color> colors = new List<System.Windows.Media.Color>();
            colors.Add(System.Windows.Media.Colors.Red);
            colors.Add(System.Windows.Media.Colors.Blue);
            colors.Add(System.Windows.Media.Colors.Green);
            BitmapPalette myPalette = new BitmapPalette(colors);

            // Creates a new empty image with the pre-defined palette
            BitmapSource image = BitmapSource.Create(
                width,
                height,
                96,
                96,
                PixelFormats.Indexed1,
                myPalette,
                pixels,
                stride);

            FileStream stream = new FileStream("new.bmp", FileMode.Create);
            BmpBitmapEncoder encoder = new BmpBitmapEncoder();
            TextBlock myTextBlock = new TextBlock();
            myTextBlock.Text = "Codec Author is: " + encoder.CodecInfo.Author.ToString();
            encoder.Frames.Add(BitmapFrame.Create(image));
            encoder.Save(stream);