Function encode_image 

pub fn encode_image<T, P, Map>(
    map: &Map,
    map_extent: &Extent2i,
) -> ImageBuffer<P, Vec<<P as Pixel>::Subpixel>>
where
    T: Into<P>,
    Map: for<'a> Get<&'a Point2i, Data = T>,
    P: Pixel + 'static,