Grass_Raster_GreyScaleService - This service converts raster map category values to their grey scale equivalents.
Operations:
default_weights - Converts map category values to their grey scale equivalents using default weightings. It is used for the map which has a grey scale color table. equal_weights - Converts map category values to their grey scale equivalents using equal weightings. ntsc_weights - Converts map category values to their grey scale equivalents using NTSC weightings. specified_weights - Converts a color raster map including the red, green, or blue components to a grey scale equivalents. Users can specify weights for each component of the input raster map.
