Function slippy_map_tiles::merc_location_to_tile_coords

pub fn merc_location_to_tile_coords(
    x: f64, 
    y: f64, 
    zoom: u8
) -> ((u32, u32), (u32, u32))

Return the x,y of a tile which (for this zoom) has this web mercator 3857 x/y, and then the x,y of the pixel within that image (presuming a 256x256 image)