Function `index_colors`

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

Reduces the colors using the supplied color_map and returns an image of the indices