Function slippy_map_tilenames::zoom_out

pub fn zoom_out(x: u32, y: u32) -> (u32, u32)

Zooms out starting from the given tile

The zoom out function, given a tile t:(x, y) corresponding to the zoomlevel z, returns the tile t_out into which the tile t is merged when zooming to the previous zoomlevel z - 1.

The actual zoomlevel is of no consequence to the function, since when zooming in the tile t_out will be split out into 4 tiles, one of which is in fact the present tile t, as per the definitions of a web slippy map.

For more info, cf. the relevant article in wiki.openstreetmap.org

Refer also to the Output section of the zoom_in function.

Arguments

• x - X current tile coordinate
• y - Y current tile coordinate

Notice how the zoomlevel is unimportant, and therefore not needed as argument, since many tile's X and Y coordinates are shared among many different zoomlevels.

Examples

extern crate slippy_map_tilenames as smt;

fn main() {
    let ((a1, b1), (c1, d1), (a2, b2), (c2, d2)) = smt::zoom_in(1,1);
    println!("+------+------+");
    println!("| {}, {} | {}, {} |", a1, b1, c1, d1 );
    println!("+------+------+");
    println!("| {}, {} | {}, {} |", a2, b2, c2, d2 );
    println!("+------+------+");
}

Unexpected Behavior

This function does not behave unexpectedly. However care should be taken in providing the tile's coordinates in input, since many tile's X and Y coordinates are shared among many different zoomlevels.

Cf. the following limit case, where zooming out from the tile (0, 0) only obtains the same tile (0, 0):

extern crate slippy_map_tilenames as smt;
 
assert_eq!(smt::zoom_out(0, 0), (0, 0));