dc-sdk/src/modules/imagery/projection/BaiduMercatorProjection.js

/**
 * @Author: Caven
 * @Date: 2021-01-30 22:41:41
 */

const EARTH_RADIUS = 6370996.81
const MC_BAND = [12890594.86, 8362377.87, 5591021, 3481989.83, 1678043.12, 0]
const LL_BAND = [75, 60, 45, 30, 15, 0]
const MC2LL = [
  [
    1.410526172116255e-8, 8.98305509648872e-6, -1.9939833816331,
    2.009824383106796e2, -1.872403703815547e2, 91.6087516669843,
    -23.38765649603339, 2.57121317296198, -0.03801003308653, 1.73379812e7,
  ],
  [
    -7.435856389565537e-9, 8.983055097726239e-6, -0.78625201886289,
    96.32687599759846, -1.85204757529826, -59.36935905485877, 47.40033549296737,
    -16.50741931063887, 2.28786674699375, 1.026014486e7,
  ],
  [
    -3.030883460898826e-8, 8.98305509983578e-6, 0.30071316287616,
    59.74293618442277, 7.357984074871, -25.38371002664745, 13.45380521110908,
    -3.29883767235584, 0.32710905363475, 6.85681737e6,
  ],
  [
    -1.981981304930552e-8, 8.983055099779535e-6, 0.03278182852591,
    40.31678527705744, 0.65659298677277, -4.44255534477492, 0.85341911805263,
    0.12923347998204, -0.04625736007561, 4.48277706e6,
  ],
  [
    3.09191371068437e-9, 8.983055096812155e-6, 0.00006995724062,
    23.10934304144901, -0.00023663490511, -0.6321817810242, -0.00663494467273,
    0.03430082397953, -0.00466043876332, 2.5551644e6,
  ],
  [
    2.890871144776878e-9, 8.983055095805407e-6, -0.00000003068298,
    7.47137025468032, -0.00000353937994, -0.02145144861037, -0.00001234426596,
    0.00010322952773, -0.00000323890364, 8.260885e5,
  ],
]
const LL2MC = [
  [
    -0.0015702102444, 1.113207020616939e5, 1.704480524535203e15,
    -1.033898737604234e16, 2.611266785660388e16, -3.51496691766537e16,
    2.659570071840392e16, -1.072501245418824e16, 1.800819912950474e15, 82.5,
  ],
  [
    8.277824516172526e-4, 1.113207020463578e5, 6.477955746671608e8,
    -4.082003173641316e9, 1.077490566351142e10, -1.517187553151559e10,
    1.205306533862167e10, -5.124939663577472e9, 9.133119359512032e8, 67.5,
  ],
  [
    0.00337398766765, 1.113207020202162e5, 4.481351045890365e6,
    -2.339375119931662e7, 7.968221547186455e7, -1.159649932797253e8,
    9.723671115602145e7, -4.366194633752821e7, 8.477230501135234e6, 52.5,
  ],
  [
    0.00220636496208, 1.113207020209128e5, 5.175186112841131e4,
    3.796837749470245e6, 9.920137397791013e5, -1.22195221711287e6,
    1.340652697009075e6, -6.209436990984312e5, 1.444169293806241e5, 37.5,
  ],
  [
    -3.441963504368392e-4, 1.113207020576856e5, 2.782353980772752e2,
    2.485758690035394e6, 6.070750963243378e3, 5.482118345352118e4,
    9.540606633304236e3, -2.71055326746645e3, 1.405483844121726e3, 22.5,
  ],
  [
    -3.218135878613132e-4, 1.113207020701615e5, 0.00369383431289,
    8.237256402795718e5, 0.46104986909093, 2.351343141331292e3,
    1.58060784298199, 8.77738589078284, 0.37238884252424, 7.45,
  ],
]

class BaiduMercatorProjection {
  constructor() {
    this.isWgs84 = false
  }

  /**
   *
   * @param point1
   * @param point2
   * @returns {number}
   */
  getDistanceByMC(point1, point2) {
    if (!point1 || !point2) {
      return 0
    }
    point1 = this.convertMC2LL(point1)
    if (!point1) {
      return 0
    }
    let x1 = this.toRadians(point1['lng'])
    let y1 = this.toRadians(point1['lat'])
    point2 = this.convertMC2LL(point2)
    if (!point2) {
      return 0
    }
    let x2 = this.toRadians(point2['lng'])
    let y2 = this.toRadians(point2['lat'])
    return this.getDistance(x1, x2, y1, y2)
  }

  /**
   * Calculate the distance between two points according to the latitude and longitude coordinates
   * @param point1
   * @param point2
   * @returns {number|*}
   */
  getDistanceByLL(point1, point2) {
    if (!point1 || !point2) {
      return 0
    }
    point1['lng'] = this.getLoop(point1['lng'], -180, 180)
    point1['lat'] = this.getRange(point1['lat'], -74, 74)
    point2['lng'] = this.getLoop(point2['lng'], -180, 180)
    point2['lat'] = this.getRange(point2['lat'], -74, 74)
    let x1 = this.toRadians(point1['lng'])
    let y1 = this.toRadians(point1['lat'])
    let x2 = this.toRadians(point2['lng'])
    let y2 = this.toRadians(point2['lat'])
    return this.getDistance(x1, x2, y1, y2)
  }

  /**
   * The plane cartesian coordinates are converted to latitude and longitude coordinates
   * @param point
   * @returns {Point|{lng: number, lat: number}}
   */
  convertMC2LL(point) {
    if (!point) {
      return { lng: 0, lat: 0 }
    }
    let lnglat = {}
    if (this.isWgs84) {
      lnglat.lng = (point.lng / 20037508.34) * 180
      let mmy = (point.lat / 20037508.34) * 180
      lnglat.lat =
        (180 / Math.PI) *
        (2 * Math.atan(Math.exp((mmy * Math.PI) / 180)) - Math.PI / 2)
      return {
        lng: lnglat['lng'].toFixed(6),
        lat: lnglat['lat'].toFixed(6),
      }
    }

    let temp = {
      lng: Math.abs(point['lng']),
      lat: Math.abs(point['lat']),
    }

    let factor = undefined
    for (let i = 0; i < MC_BAND.length; i++) {
      if (temp['lat'] >= MC_BAND[i]) {
        factor = MC2LL[i]
        break
      }
    }
    lnglat = this.convertor(point, factor)
    return {
      lng: lnglat['lng'].toFixed(6),
      lat: lnglat['lat'].toFixed(6),
    }
  }

  /**
   * The latitude and longitude coordinates are converted to plane cartesian coordinates
   * @param point
   * @returns {{lng: number, lat: number}|*}
   */
  convertLL2MC(point) {
    if (!point) {
      return { lng: 0, lat: 0 }
    }
    if (
      point['lng'] > 180 ||
      point['lng'] < -180 ||
      point['lat'] > 90 ||
      point['lat'] < -90
    ) {
      return point
    }

    if (this.isWgs84) {
      let mercator = {}
      let earthRad = 6378137.0
      mercator.lng = ((point.lng * Math.PI) / 180) * earthRad
      let a = (point.lat * Math.PI) / 180
      mercator.lat =
        (earthRad / 2) * Math.log((1.0 + Math.sin(a)) / (1.0 - Math.sin(a)))

      return {
        lng: parseFloat(mercator['lng'].toFixed(2)),
        lat: parseFloat(mercator['lat'].toFixed(2)),
      }
    }

    point['lng'] = this.getLoop(point['lng'], -180, 180)
    point['lat'] = this.getRange(point['lat'], -74, 74)
    let temp = { lng: point['lng'], lat: point['lat'] }
    let factor = undefined
    for (let i = 0; i < LL_BAND.length; i++) {
      if (temp['lat'] >= LL_BAND[i]) {
        factor = LL2MC[i]
        break
      }
    }
    if (!factor) {
      for (let i = 0; i < LL_BAND.length; i++) {
        if (temp['lat'] <= -LL_BAND[i]) {
          factor = LL2MC[i]
          break
        }
      }
    }
    let mc = this.convertor(point, factor)
    return {
      lng: parseFloat(mc['lng'].toFixed(2)),
      lat: parseFloat(mc['lat'].toFixed(2)),
    }
  }

  /**
   *
   * @param fromPoint
   * @param factor
   * @returns {{lng: *, lat: *}}
   */
  convertor(fromPoint, factor) {
    if (!fromPoint || !factor) {
      return { lng: 0, lat: 0 }
    }
    let x = factor[0] + factor[1] * Math.abs(fromPoint['lng'])
    let temp = Math.abs(fromPoint['lat']) / factor[9]
    let y =
      factor[2] +
      factor[3] * temp +
      factor[4] * temp * temp +
      factor[5] * temp * temp * temp +
      factor[6] * temp * temp * temp * temp +
      factor[7] * temp * temp * temp * temp * temp +
      factor[8] * temp * temp * temp * temp * temp * temp
    x *= fromPoint['lng'] < 0 ? -1 : 1
    y *= fromPoint['lat'] < 0 ? -1 : 1
    return {
      lng: x,
      lat: y,
    }
  }

  /**
   *
   * @param x1
   * @param x2
   * @param y1
   * @param y2
   * @returns {number}
   */
  getDistance(x1, x2, y1, y2) {
    return (
      EARTH_RADIUS *
      Math.acos(
        Math.sin(y1) * Math.sin(y2) +
          Math.cos(y1) * Math.cos(y2) * Math.cos(x2 - x1)
      )
    )
  }

  /**
   *
   * @param deg
   * @returns {number}
   */
  toRadians(deg) {
    return (Math.PI * deg) / 180
  }

  /**
   *
   * @param rad
   * @returns {number}
   */
  toDegrees(rad) {
    return (180 * rad) / Math.PI
  }

  /**
   *
   * @param v
   * @param a
   * @param b
   * @returns {number}
   */
  getRange(v, a, b) {
    if (a != null) {
      v = Math.max(v, a)
    }
    if (b != null) {
      v = Math.min(v, b)
    }
    return v
  }

  /**
   *
   * @param v
   * @param a
   * @param b
   * @returns {*}
   */
  getLoop(v, a, b) {
    while (v > b) {
      v -= b - a
    }
    while (v < a) {
      v += b - a
    }
    return v
  }

  /**
   *
   * @param point
   * @returns {{lng: number, lat: number}|*}
   */
  lngLatToMercator(point) {
    return this.convertLL2MC(point)
  }

  /**
   *
   * @param point
   * @returns {{x: (number|*), y: (number|*)}}
   */
  lngLatToPoint(point) {
    let mercator = this.convertLL2MC(point)
    return {
      x: mercator['lng'],
      y: mercator['lat'],
    }
  }

  /**
   * WebMercator transforms to latitude and longitude
   * @param point
   * @returns {Point|{lng: number, lat: number}}
   */
  mercatorToLngLat(point) {
    return this.convertMC2LL(point)
  }

  /**
   *
   * @param point
   * @returns {Point|{lng: number, lat: number}}
   */
  pointToLngLat(point) {
    let mercator = { lng: point.x, lat: point.y }
    return this.convertMC2LL(mercator)
  }

  /**
   * Latitude and longitude coordinates  transforms to  pixel coordinates
   * @param point
   * @param zoom
   * @param mapCenter
   * @param mapSize
   * @returns {{x: number, y: number}}
   */
  pointToPixel(point, zoom, mapCenter, mapSize) {
    if (!point) {
      return { x: 0, y: 0 }
    }
    point = this.lngLatToMercator(point)
    let zoomUnits = this.getZoomUnits(zoom)
    let x = Math.round(
      (point['lng'] - mapCenter['lng']) / zoomUnits + mapSize.width / 2
    )
    let y = Math.round(
      (mapCenter['lat'] - point['lat']) / zoomUnits + mapSize.height / 2
    )
    return { x, y }
  }

  /**
   * Pixel coordinates transforms to latitude and longitude coordinates
   * @param pixel
   * @param zoom
   * @param mapCenter
   * @param mapSize
   * @returns {Point|{lng: number, lat: number}}
   */
  pixelToPoint(pixel, zoom, mapCenter, mapSize) {
    if (!pixel) {
      return { lng: 0, lat: 0 }
    }
    let zoomUnits = this.getZoomUnits(zoom)
    let lng = mapCenter['lng'] + zoomUnits * (pixel.x - mapSize.width / 2)
    let lat = mapCenter['lat'] - zoomUnits * (pixel.y - mapSize.height / 2)
    let point = { lng, lat }
    return this.mercatorToLngLat(point)
  }

  /**
   *
   * @param zoom
   * @returns {number}
   */
  getZoomUnits(zoom) {
    return Math.pow(2, 18 - zoom)
  }
}

export default BaiduMercatorProjection