BitmapFrame Class

            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("empty.tif", FileMode.Create);
            TiffBitmapEncoder encoder = new TiffBitmapEncoder();
            TextBlock myTextBlock = new TextBlock();
            myTextBlock.Text = "Codec Author is: " + encoder.CodecInfo.Author.ToString();
            encoder.Frames.Add(BitmapFrame.Create(image));
            MessageBox.Show(myPalette.Colors.Count.ToString());
            encoder.Save(stream);

Stream pngStream = new System.IO.FileStream("smiley.png", FileMode.Open, FileAccess.ReadWrite, FileShare.ReadWrite);
PngBitmapDecoder pngDecoder = new PngBitmapDecoder(pngStream, BitmapCreateOptions.PreservePixelFormat, BitmapCacheOption.Default);
BitmapFrame pngFrame = pngDecoder.Frames[0];
InPlaceBitmapMetadataWriter pngInplace = pngFrame.CreateInPlaceBitmapMetadataWriter();
if (pngInplace.TrySave() == true)
{ pngInplace.SetQuery("/Text/Description", "Have a nice day."); }
pngStream.Close();