Convert PDF to an image using a dither matrix

using (FileStream fs = new FileStream(@"..\..\input.pdf", FileMode.Open, FileAccess.Read))
{
    Document d = new Document(fs);

    int[][] DitherMatrix = new int[][] {
            new int[] { 9, 9, 7 }, 
            new int[] { 4, 1, 0 }, 
            new int[] { 0, 5, 2 }};
    Page page = d.Pages[0];

    Bitmap bitmap = new Bitmap((int)page.Width, (int)page.Height);

    ConvertToTiffOptions options = new ConvertToTiffOptions();

    //set a dithering matrix
    options.DitherMatrix = DitherMatrix;

    using (MemoryStream ms = new MemoryStream())
    {
        using (Graphics graphics = Graphics.FromImage(bitmap))
        {
            graphics.SmoothingMode = SmoothingMode.AntiAlias;
            graphics.Clear(Color.White);
            page.ConvertToTiff(ms, options);
        }
        bitmap = new Bitmap(ms, false);
        bitmap.Save(@"..\..\output.bmp");
    }
}