Function dither

pub fn dither<Pix, Map>(image: &mut ImageBuffer<Pix, Vec<u8>>, color_map: &Map)
where
    Map: ColorMap<Color = Pix> + ?Sized,
    Pix: Pixel<Subpixel = u8> + 'static,

Reduces the colors of the image using the supplied color_map while applying Floyd-Steinberg dithering to improve the visual conception