@loaders.gl/mvt/src/lib/vector-tiler/tile-to-geojson.ts

Loader for Mapbox Vector Tiles

// loaders.gl
// SPDX-License-Identifier: MIT
// Copyright (c) vis.gl contributors
// Forked from https://github.com/mapbox/geojson-vt under compatible ISC license

import {ProtoTile} from './proto-tile';
import {Feature, GeoJSONTable} from '@loaders.gl/schema';

import {projectToLngLat, convertToLocalCoordinates} from '../utils/geometry-utils';

// eslint-disable-next-line max-statements, complexity
export function convertTileToGeoJSON(
  protoTile: ProtoTile,
  props: {
    coordinates: 'EPSG:4326' | 'wgs84' | 'local';
    tileIndex: {x: number; y: number; z: number};
    extent: number;
  }
): GeoJSONTable | null {
  const features: Feature[] = [];
  for (const rawFeature of protoTile.protoFeatures) {
    if (!rawFeature || !rawFeature.geometry) {
      // eslint-disable-next-line no-continue
      continue;
    }

    let type:
      | 'Point'
      | 'MultiPoint'
      | 'LineString'
      | 'MultiLineString'
      | 'Polygon'
      | 'MultiPolygon';

    let coordinates: any;

    // raw geometry
    switch (rawFeature.simplifiedType) {
      case 1:
        if (rawFeature.geometry.length === 1) {
          type = 'Point';
          coordinates = rawFeature.geometry[0];
        } else {
          type = 'MultiPoint';
          coordinates = rawFeature.geometry;
        }
        break;
      case 2:
        if (rawFeature.geometry.length === 1) {
          type = 'LineString';
          coordinates = rawFeature.geometry[0];
        } else {
          type = 'MultiLineString';
          coordinates = rawFeature.geometry;
        }
        break;
      case 3:
        if (rawFeature.geometry.length > 1) {
          type = 'MultiPolygon';
          coordinates = [rawFeature.geometry];
        } else {
          type = 'Polygon';
          coordinates = rawFeature.geometry;
        }
        break;
      default:
        throw new Error(`${rawFeature.simplifiedType}is not a valid simplified type`);
    }

    switch (props.coordinates) {
      case 'EPSG:4326':
      case 'wgs84':
        projectToLngLat(coordinates, props.tileIndex, props.extent);
        break;
      default:
        convertToLocalCoordinates(coordinates, props.extent);
        break;
    }

    const feature: Feature = {
      type: 'Feature',
      geometry: {
        type,
        coordinates
      },
      properties: rawFeature.tags || {},
      id: rawFeature.id
    };

    features.push(feature);
  }

  if (features.length === 0) {
    return null;
  }

  const table: GeoJSONTable = {
    shape: 'geojson-table',
    type: 'FeatureCollection',
    features
  };

  return table;
}