The Desaturate submenu contains operations that turn an image into a Grayscale representation, using different methods.
قسمت 8.29, “Color to Gray”
قسمت 8.30, “Desaturate”
قسمت 8.24, “Mono Mixer”
قسمت 8.32, “Sepia”
You can access this command from the main menu through Colors → Desaturate.