markiearnold / maplibre-provider

@com-tiles/maplibre-provider

The @com-tiles/maplibre-provider package can be used to access a COMTiles archive hosted on an cloud object storage like AWS S3 directly from the browser.
To display the map tiles from a COMTiles archive based on the MapLibre web mapping library register the MapLibreComProvider before creating a MapLibre map instance.
For how to use the MapLibreComProvider class via the script tag see the following snippet.

<script src="https://unpkg.com/[email protected]/dist/maplibre-gl.js"></script>
<link href="https://unpkg.com/[email protected]/dist/maplibre-gl.css" rel="stylesheet" />
<script src="https://unpkg.com/@com-tiles/maplibre-provider@latest/dist/maplibreComtProvider.js"></script>

<script>
    comtiles.MapLibreComtProvider.register();
    const map = new maplibregl.Map({
        container: "map",
        style: "http://localhost:4711/assets/style.json",
        center: [0, 0],
        zoom: 0,
    });
</script>

For how to use the MapLibreComProvider class via the import statement see the following snippet.

import  { MapLibreComtProvider } from "@com-tiles/maplibre-provider";

MapLibreComtProvider.register();
const map = new maplibregl.Map({...});

Make sure that the URL of the COMTiles archive is added to the sources list in the style definition (style.json) of the map with a comt:// prefix like in the following example

"test-source": {
    "type": "vector",
    "tiles": [
      "comt://http://0.0.0.0:9000/comtiles/test.comt/{z}/{x}/{y}"
    ]
    "maxzoom": 14
}

Per default the individual tile requests get batched to improve performance and in particular to reduce the storage costs.
This can reduce the number of tile requests up to 90%.
To disable this optimization create the MapLibreComtProvider with the following options

MapLibreComtProvider.register(TileContent.MVT, TileFetchStrategy.SINGLE);

The @com-tiles/maplibre-provider package has currently the following limitations regarding the support of the COMTiles specification

• The only supported TileMatrixCRS is WebMercatorQuad
• Only Mapbox vector tiles are supported as content of a map tile and no raster formats (PNG, WebP)
• The only supported space-filling curve type for the order of the index fragments and tiles is row-major
• Only index fragments can be loaded after the initial fetch. So with the first initial fetch all the unfragmented part of the index has to be fetched and can't be lazy loaded.