web-mercator-tiles

Calculate map tiles for given map extent and zoom level. Considering map extent coordinates are in sperical (web) mercator projection.

installation

npm install web-mercator-tiles

usage

var webMercatorTiles = require('web-mercator-tiles');
function: webMercatorTiles(extent,zoom)
parameters:
  extent: map extent of window or div in spherical mercator projeection (meters)
    {
      left: coordinate in meter,
      right: coordinate in meter,
      bottom: coordinate in meter,
      top: coordinate in meter
    }
  zoom: zoom level as integer
output: array of tiles object, where tile object is 
  {
    X: tile number in x direction
    Y: tile number in y direction 
    Z: tile number for zoom
    top: top of tile image position in window as pixel
    left: left of tile image position in window as pixel
  }

TileExtent, a static funtion to get tile extent in web mercator coordinates

param: {z: zoom leve, x: x tile no, y: y tile no}

example

var webMercatorTiles = require('web-mercator-tiles'),
  mapExtent = {
    left:-7929831.7499857,
    bottom:5227055.1160079,
    right:-7910263.8707475,
    top:5236839.0556271
  },
  zoom = 12;
tiles = webMercatorTiles(mapExtent,zoom);
// tiles are
/*
[ { X: 1237, Y: 1512, Z: 12, top: -192, left: -129 },
  { X: 1237, Y: 1513, Z: 12, top: 64, left: -129 },
  { X: 1238, Y: 1512, Z: 12, top: -192, left: 127 },
  { X: 1238, Y: 1513, Z: 12, top: 64, left: 127 },
  { X: 1239, Y: 1512, Z: 12, top: -192, left: 383 },
  { X: 1239, Y: 1513, Z: 12, top: 64, left: 383 } ]
*/

// Tile Extent
var tile = {z:12, x: 2953, y: 1697}
var extent = webMercatorTiles.TileExtent(tile)

// extent is
/*
{
  left: 8844681.416934315,
  right: 8854465.356554817,
  bottom: 3434162.806796398,
  top: 3443946.746416901,
  res: 38.21851414258813
}
*/

Similar

Check map-the-tiles for projections other than spherical mercator, and having spherical mecator as default projection.

developing

Once you run

npm isntall

then for running test

npm run test

to create build

npm run build

license

This project is licensed under the terms of the MIT license.