vector-tile-esm

!tests

Reads [Mapbox Vector Tiles][] and allows access to the layers and features.

This module is a fork of [vector-tile-js][], with several key changes:
- Code is set up for ESM import, rather than CJS require. This allows it
to be imported dynamically (e.g., on [Observable][]) without depending on a
third-party bundling service such as [bundle.run][]
- The VectorTileFeature.toGeoJSON() method behaves very differently, returning
pixel coordinates within a tile, rather than assuming Web Mercator and
attempting to back-project to longitude and latitude
- The dependence on the [point-geometry][] module has been removed

[Mapbox Vector Tiles]: https://github.com/mapbox/vector-tile-spec
[vector-tile-js]: https://github.com/mapbox/vector-tile-js
[Observable]: https://observablehq.com
[bundle.run]: https://bundle.run
[point-geometry]: https://github.com/mapbox/point-geometry

Example

``js
import { VectorTile } from 'vector-tile-esm';
import Protobuf from 'pbf-esm';

var tile = new VectorTile(new Protobuf(data));

// Contains a map of all layers
tile.layers;

var landuse = tile.layers.landuse;

// Number of features in this layer
landuse.length;

// Returns the first feature
landuse.feature(0);
`

API Reference

- new VectorTile(protobuf[, end]) —
parses the vector tile data contained in the given [Protobuf][] object,
saving resulting layers in the created object as a layers property.
Optionally accepts end index.

[Protobuf]: https://github.com/mapbox/pbf

$3

- layers (Object) — an object containing parsed layers in the form of
{: , ...}, where each layer is a VectorTileLayer object.

VectorTileLayer

An object that contains the data for a single vector tile layer.

$3

- version (Number, default: 1)
- name (String) — layer name
- extent (Number, default: 4096) — tile extent size
- length (Number) — number of features in the layer

$3

- feature(i) — get a feature (VectorTileFeature) by the given index
from the layer.
- toGeoJSON(size[, sx, sy]) — Return a GeoJSON FeatureCollection
representing all the features in the layer. See the corresponding method of
VectorTileFeature for the parameters

VectorTileFeature

An object that contains the data for a single feature.

$3

- type (Number) — type of the feature (also see VectorTileFeature.types)
- extent (Number) — feature extent size
- id (Number) — feature identifier, if present
- properties (Object) — object literal with feature properties

$3

- loadGeometry() — parses feature geometry and returns an array of
point objects, with each point having x and y properties
- bbox() — calculates and returns the bounding box of the feature in
the form [x1, y1, x2, y2]
- toGeoJSON(size[, sx, sy]) — returns a GeoJSON representation of the
feature.
- size — side length of the (square) area over which the tile's
features will be rendered. Default: the .extent property of the layer
- sx, sy` — optionally specify the origin of the output coordinates
within the (size x size) rendered area of the full tile.