grayscale.cs

string outputFileTemplate = Path.Combine("c:\output", "converted-page-{0}.png");
SavePageStream getPageStream = page => new FileStream(string.Format(outputFileTemplate, page), FileMode.Create);
using (Converter converter = new Converter("sample.pdf"))
{
    ImageConvertOptions options = new ImageConvertOptions
    {
        Format = ImageFileType.Png,
        FlipMode = ImageFlipModes.FlipY,
        Brightness = 50,
        Contrast = 50,
        Gamma = 0.5F,
        Grayscale = true,
        HorizontalResolution = 300,
        VerticalResolution = 100
    };
     
    converter.Convert(getPageStream, options);
}