@loaders.gl/mvt/src/lib/vector-tiler/features/proto-feature.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

export type ProtoFeature = {
  type: 'Point' | 'MultiPoint' | 'LineString' | 'MultiLineString' | 'Polygon' | 'MultiPolygon';
  simplifiedType: 1 | 2 | 3;
  geometry: any[];

  // book keeping
  id?: string;
  tags?: Record<string, unknown>;

  /** spatial extents */
  minX: number;
  /** spatial extents */
  maxX: number;
  /** spatial extents */
  minY: number;
  /** spatial extents */
  maxY: number;
};

export type GeoJSONTileGeometry =
  | GeoJSONTilePointGeometry
  | GeoJSONTileLineGeometry
  | GeoJSONTilePolygonGeometry;

export type GeoJSONTilePointGeometry = {
  simplifiedType: 1;
  geometry: number[];
};

export type GeoJSONTileLineGeometry = {
  simplifiedType: 1;
  geometry: number[][];
};

export type GeoJSONTilePolygonGeometry = {
  simplifiedType: 1;
  geometry: number[][][];
};

export function createProtoFeature(
  id: any,
  type: 'Point' | 'MultiPoint' | 'LineString' | 'MultiLineString' | 'Polygon' | 'MultiPolygon',
  geometry: any[],
  tags
): ProtoFeature {
  const feature: ProtoFeature = {
    // eslint-disable-next-line
    id: id == null ? null : id,
    type,
    simplifiedType: undefined!, // TODO
    geometry,
    tags,
    minX: Infinity,
    minY: Infinity,
    maxX: -Infinity,
    maxY: -Infinity
  };

  // TODO break out into separate function
  switch (type) {
    case 'Point':
    case 'MultiPoint':
    case 'LineString':
      calcLineBBox(feature, geometry);
      break;

    case 'MultiLineString':
      for (const line of geometry) {
        calcLineBBox(feature, line);
      }
      break;

    case 'Polygon':
      // the outer ring (ie [0]) contains all inner rings
      calcLineBBox(feature, geometry[0]);
      break;

    case 'MultiPolygon':
      for (const polygon of geometry) {
        // the outer ring (ie [0]) contains all inner rings
        calcLineBBox(feature, polygon[0]);
      }
      break;

    default:
      throw new Error(String(type));
  }

  return feature;
}

function calcLineBBox(feature, geometry) {
  for (let i = 0; i < geometry.length; i += 3) {
    feature.minX = Math.min(feature.minX, geometry[i]);
    feature.minY = Math.min(feature.minY, geometry[i + 1]);
    feature.maxX = Math.max(feature.maxX, geometry[i]);
    feature.maxY = Math.max(feature.maxY, geometry[i + 1]);
  }
}