ol-extent/src/source/Baidu.js

a JavaScript library for openlayers extent

import ol from 'openlayers'
import { getRandom } from '../utils'

class Baidu extends ol.source.TileImage {
  static ATTRIBUTION = new ol.Attribution({
    html: '© ' +
    '<a href="http://map.baidu.com/">百度地图</a> ' +
    'contributors.'
  });
  constructor (options = {}) {
    let attributions = '';
    if (options.attributions !== undefined) {
      attributions = options.attributions;
    } else {
      attributions = [Baidu.ATTRIBUTION];
    }
    options.projection = options['projection'] ? options.projection : 'EPSG:3857';
    const crossOrigin = options.crossOrigin !== undefined ? options.crossOrigin : 'anonymous';
    let url = options.url !== undefined ? options.url : 'http://online{0-3}.map.bdimg.com/onlinelabel/?qt=tile&x={x}&y={y}&z={z}&styles={styles}&udt=20170607&scaler=1&p=1';
    const hidpi = options.hidpi || (window.devicePixelRatio || (window.screen.deviceXDPI / window.screen.logicalXDPI)) > 1;
    url = url.replace('{styles}', (hidpi ? 'ph' : 'pl'));
    let tileUrlFunction = options.tileUrlFunction ? options.tileUrlFunction : undefined;
    if (!tileUrlFunction) {
      tileUrlFunction = function (tileCoord) {
        let [z, y, x] = [tileCoord[0], tileCoord[2], tileCoord[1]];
        if (x < 0) {
          x = 'M' + (-x)
        }
        if (y < 0) {
          y = 'M' + (-y)
        }
        return url.replace('{0-3}', getRandom(0, 3)).replace('{x}', (x).toString()).replace('{y}', y.toString()).replace('{z}', (z).toString())
      }
    }
    const levels = options['levels'] ? options['levels'] : 19;
    const resolutions = [];
    for (let z = 0; z < levels; z++) {
      resolutions[z] = Math.pow(2, levels - 1 - z);
    }
    const tileGrid = new ol.tilegrid.TileGrid({
      tileSize: options['tileSize'] ? options['tileSize'] : 256,
      origin: (options['origin'] ? options['origin'] : [0, 0]),
      extent: (options['extent'] ? options['extent'] : undefined),
      resolutions: resolutions,
      minZoom: ((options['minZoom'] && typeof options['minZoom'] === 'number') ? options['minZoom'] : 0)
    });
    super({
      tileGrid: tileGrid,
      attributions: attributions,
      cacheSize: options.cacheSize,
      projection: options.projection,
      crossOrigin: crossOrigin,
      opaque: options.opaque !== undefined ? options.opaque : true,
      maxZoom: options.maxZoom !== undefined ? options.maxZoom : 19,
      reprojectionErrorThreshold: options.reprojectionErrorThreshold,
      tileUrlFunction: tileUrlFunction,
      url: url,
      wrapX: options.wrapX,
      tilePixelRatio: hidpi ? 2 : 1
    })
  }
}

export default Baidu