You can make a image black and white with various methods, one is setting the ColorType to BiLevel:
You can create a sepia-tone image with the SepiaTone method of MagickImage:
using (MagickImage logo = new MagickImage("logo:")) { logo.ColorType = ColorType.Bilevel; logo.Write("\logo.png"); }
using (MagickImage logo = new MagickImage("logo:")) { logo.SepiaTone(65); logo.Write("logo.png"); }