https://github.com/mapbox/tilelive-vector

Implements the tilelive API for rendering mapnik vector tiles to raster images.
https://github.com/mapbox/tilelive-vector

Last synced: about 1 month ago
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Implements the tilelive API for rendering mapnik vector tiles to raster images.

• Host: GitHub
• URL: https://github.com/mapbox/tilelive-vector
• Owner: mapbox
• License: bsd-3-clause
• Created: 2013-03-07T16:55:35.000Z (over 11 years ago)
• Default Branch: master
• Last Pushed: 2024-05-20T20:17:39.000Z (4 months ago)
• Last Synced: 2024-07-19T06:05:26.529Z (about 2 months ago)
• Language: JavaScript
• Size: 9.14 MB
• Stars: 71
• Watchers: 122
• Forks: 44
• Open Issues: 25
• Metadata Files:
  • Readme: README.md
  • Changelog: CHANGELOG.md
  • License: LICENSE.md

Awesome Lists containing this project

• awesome-vector-tiles - tilelive-vector - Implements [Tilelive API](https://github.com/mapbox/tilelive.js/blob/master/API.md) for reading vector tiles and rendering to image tiles in Node.js. (Parsers & Generators)

README

        
tilelive-vector

---------------

Implements the tilelive API for rendering mapnik vector tiles to raster images.

[![Build Status](https://travis-ci.com/mapbox/tilelive-vector.svg?branch=master)](http://travis-ci.com/mapbox/tilelive-vector)

[![Coverage Status](https://coveralls.io/repos/mapbox/tilelive-vector/badge.svg?branch=master&service=github)](https://coveralls.io/github/mapbox/tilelive-vector?branch=master)

### new Vector(options, callback)

- *xml*: a Mapnik XML string that will be used to render vector tiles.

- *source*: Optional, a uri string suitable for use with `tilelive.load()`. This is fallback source that will be used if no source is found as part of the Mapnik XML parameters.

- *base*: Optional, basepath for Mapnik map. Defaults to `__dirname`.

- *format*: Optional, target output format. Defaults to `png8:m=h`.

- *scale*: Optional, Mapnik scale factor. Defaults to `1`.

### Code concepts

- *Backend z/x/y*: a request for a raster tile at, say, 3/3/3 does not always mean 3/3/3 is requested from the backend source. The z/x/y requested from the backend source is referred in code by `bz/bx/by` and generally represent the same or lower zoom level. This allows for features like *overzooming*, *maskLevel tiles*, and *scale factor adjustment*.

- *Overzooming*: if a tile beyond the `maxzoom` of the backend is requested, Vector will attempt to render the tile using the parent of the request at `maxzoom`.

- *maskLevel tiles*: to avoid requiring many duplicate or empty vector tiles to be generated at high zoom levels, the backend source can specify a `maskLevel`. If a vector tile is not initially found at some `z > maskLevel`, Vector will issue an additional request to the backend using the parent tile of of the request at `maskLevel`. This allows a lower zoom level to "backfill" high zoom levels.

- *Scale factor adjustment*: the scale argument decrements the backend zoom level such that the requested tile is the visual equivalent (when viewed on the proper dpi device) of its parent counterpart. For example, `scale: 2` decrements `bz` by 1, `scale: 4` decrements by 2, and so on.

### Backend headers

The Backend and Vector sources set the `x-vector-backend-object` header to indicate the type of backend source tile loaded. Possible values:

value | description

--- | ---

empty | backend returned no tile

fillzoom | tile from the fillzoom of the backend (backfilled from a lower zoom)

overzoom | tile from the maxzoom of the backend (overzoomed)

default | normal tile

## Bonus constructors

There are two additional constructors provided for slightly different workflows for loading vector sources.

### Vector.tm2z(uri, callback)

Load a vector source from a `uri` (filepath or HTTP url) to a [tm2](https://github.com/mapbox/tm2)-generated tm2z style package.

### Vector.xray(options, callback)

Load a vector source with autogenerated data inspection ("xray") styles. `xml` is not required -- only the `uri` to a vector source backend is necessary.