itowns/lib/Source/CopcSource.js

A JS/WebGL framework for 3D geospatial data visualization

import proj4 from 'proj4';
import { Binary, Info, Las } from 'copc';
import { Extent } from '@itowns/geographic';
import Fetcher from "../Provider/Fetcher.js";
import LASParser from "../Parser/LASParser.js";
import Source from "./Source.js";
import * as THREE from 'three';

/**
 * @param {function(number, number):Promise<Uint8Array>} fetcher
 */
async function getHeaders(fetcher) {
  const header = Las.Header.parse(await fetcher(0, Las.Constants.minHeaderLength));
  const vlrs = await Las.Vlr.walk(fetcher, header);

  // info VLR: required by COPC
  const infoVlr = Las.Vlr.find(vlrs, 'copc', 1);
  if (!infoVlr) {
    return Promise.reject('COPC info VLR is required');
  }
  const info = Info.parse(await Las.Vlr.fetch(fetcher, infoVlr));

  // OGC Coordinate System WKT: required by LAS1.4
  const wktVlr = Las.Vlr.find(vlrs, 'LASF_Projection', 2112);
  if (!wktVlr) {
    return Promise.reject('LAS1.4 WKT VLR is required');
  }
  const wkt = Binary.toCString(await Las.Vlr.fetch(fetcher, wktVlr));

  // Extra bytes: optional by LAS1.4
  const ebVlr = Las.Vlr.find(vlrs, 'LASF_Spec', 4);
  const eb = ebVlr ? Las.ExtraBytes.parse(await Las.Vlr.fetch(fetcher, ebVlr)) : [];
  return {
    header,
    info,
    wkt,
    eb
  };
}

/**
 * A source for [Cloud Optimised Point Cloud](https://copc.io/) (COPC) data.
 * Such data consists of a [LAZ 1.4](https://www.ogc.org/standard/las/) file
 * that stores compressed points data organized in a clustered octree.
 *
 * A freshly created source fetches and parses portions of the file
 * corresponding to the LAS 1.4 header, all the Variable Length Record (VLR)
 * headers as well the following VLRs:
 * - COPC [`info`](https://copc.io/#info-vlr) record (mandatory)
 * - LAS 1.4 `OGC Coordinate System WKT` record (mandatory, see [Las 1.4
 *   spec](https://portal.ogc.org/files/?artifact_id=74523))
 * - LAS 1.4 `Extra Bytes` record (optional, see [Las 1.4
 *   spec](https://portal.ogc.org/files/?artifact_id=74523))
 *
 * @extends {Source}
 *
 * @property {boolean} isCopcSource - Read-only flag to check that a given
 * object is of type CopcSource.
 * @property {Object} header - LAS header of the source.
 * @property {Object[]} eb - List of headers of each Variable Length Records
 * (VLRs).
 * @property {Object} info - COPC `info` VLR.
 * @property {number[]} info.cube - Bounding box of the octree as a 6-elements.
 * tuple `[minX, minY, minZ, maxX, maxY, maxZ]`. Computed from `center_x`,
 * `center_y`, `center_z` and `halfSize` properties.
 * @property {Object} info.rootHierarchyPage - Hierarchy page of the root node.
 * @property {number} info.rootHierarchyPage.pageOffset - Absolute Offset to the
 * root node data chunk.
 * @property {number} info.rootHierarchyPage.pageOffset - Size (in bytes) of the
 * root node data chunk.
 * @property {number[]} gpsTimeRange - A 2-element tuple denoting the minimum
 * and maximum values of attribute `gpsTime`.
 */
class CopcSource extends Source {
  /**
   * @param {Object} config - Source configuration
   * @param {string} config.url - URL of the COPC resource.
   * @param {8 | 16} [config.colorDepth=16] - Encoding of the `color`
   * attribute. Either `8` or `16` bits.
   * @param {string} [config._lazPerfBaseUrl] - (experimental) Overrides base
   * url of the `las-zip.wasm` file of the `laz-perf` library.
   * @param {string} [config.crs='EPSG:4326'] - Native CRS of the COPC
   * ressource. Note that this is not for now inferred from the COPC header.
   * @param {RequestInit} [config.networkOptions] - Fetch options (passed
   * directly to `fetch()`), see [the syntax for more information](
   * https://developer.mozilla.org/en-US/docs/Web/API/WindowOrWorkerGlobalScope/fetch#Syntax).
   * @param {Object} [config.attribution] - Attribution of the data.
   */
  constructor(config) {
    super(config);
    this.isCopcSource = true;
    this.parser = LASParser.parseChunk;
    this.fetcher = Fetcher.arrayBuffer;
    this.colorDepth = config.colorDepth ?? 16;
    const get = (/** @type {number} */begin, /** @type {number} */end) => this.fetcher(this.url, {
      ...this.networkOptions,
      headers: {
        ...this.networkOptions.headers,
        range: `bytes=${begin}-${end - 1}`
      }
    }).then(buffer => new Uint8Array(buffer));
    this.whenReady = getHeaders(get).then(metadata => {
      this.header = metadata.header;
      this.info = metadata.info;
      this.eb = metadata.eb;
      proj4.defs('unknown', metadata.wkt);
      let projCS;
      if (proj4.defs('unknown').type === 'COMPD_CS') {
        console.warn('CopcSource: compound coordinate system is not yet supported.');
        projCS = proj4.defs('unknown').PROJCS;
      } else {
        projCS = proj4.defs('unknown');
      }
      this.crs = projCS.title || projCS.name || 'EPSG:4326';
      if (!(this.crs in proj4.defs)) {
        proj4.defs(this.crs, projCS);
      }
      const bbox = new THREE.Box3();
      bbox.min.fromArray(this.info.cube, 0);
      bbox.max.fromArray(this.info.cube, 3);
      this.extent = Extent.fromBox3(this.crs, bbox);
      return this;
    });
  }
}
export default CopcSource;