Fix google map offsets in china

plugins/fix-china-map-offset.js

@@ -0,0 +1,313 @@
+// ==UserScript==
+// @id             iitc-plugin-fix-china-map-offset
+// @name           IITC plugin: Fix maps offsets in China
+// @category       Tweaks
+// @version        0.2.0.@@DATETIMEVERSION@@
+// @description    [@@BUILDNAME@@-@@BUILDDATE@@] Show correct maps for China user by applying offset tweaks.
+@@METAINFO@@
+// ==/UserScript==
+
+@@PLUGINSTART@@
+
+// PLUGIN START ////////////////////////////////////////////////////////
+
+// use own namespace for plugin
+window.plugin.fixChinaOffset = {};
+
+// Before understanding how this plugin works, you should know 3 points:
+//
+//   Point1.
+//     The coordinate system of Ingress is WGS-84.
+//     However, the tiles of Google maps (except satellite map) and some other maps
+//     in China have offsets (base on GCJ-02 coordinate system) by China policy.
+//     That means, if you request map tiles by giving GCJ-02 position, you
+//     will get the correct map.
+//
+//   Point2.
+//     Currently there are no easy algorithm to transform from GCJ-02 to WGS-84,
+//     but we can easily transform data from WGS-84 to GCJ-02.
+//
+//   Point3.
+//     When using, for example, Google maps in IITC, the layer structure looks like this:
+//      --------------------------
+//     |    Other Leaflet layers  |  (Including portals, links, fields, and so on)
+//      --------------------------
+//     | L.GridLayer.GoogleMutant |  (Only for controling)
+//      --------------------------
+//     |      Google Map layer    |  (Generated by Google Map APIs, for rendering maps)
+//      --------------------------
+//
+//     When users are interacting with L.GridLayer.GoogleMutant (for example, dragging, zooming),
+//     L.GridLayer.GoogleMutant will perform the same action on the Google Map layer using Google
+//     Map APIs.
+//
+// So, here is the internal of the plugin:
+//
+// The plugin overwrites behaviours of L.GridLayer.GoogleMutant. When users are dragging the map,
+// L.GridLayer.GoogleMutant will pass offseted positions to Google Map APIs (WGS-84 to GCJ-02).
+// So Google Map APIs will render a correct map.
+//
+// The offset between Google maps and Ingress objects can also be fixed by applying
+// WGS-84 to GCJ-02 transformation on Ingress objects. However we cannot simply know
+// the requesting bounds of Ingress objects because we cannot transform GCJ-02 to
+// WGS-84. As a result, the Ingress objects on maps would be incomplete.
+//
+// The algorithm of transforming WGS-84 to GCJ-02 comes from:
+// https://on4wp7.codeplex.com/SourceControl/changeset/view/21483#353936
+// There is no official algorithm because it is classified information.
+//
+// Here we use the PRCoords implementation of this algorithm, which contains
+// a more careful yet still rough "China area" check in "insane_is_in_china.js".
+// Comments and code style have been adapted, mainly to remove profanity.
+// https://github.com/Artoria2e5/PRCoords
+//
+// Correction is made for maps that have the parameter
+//   needFixChinaOffset: true
+// in options. For an example of work, see Leaflet.GoogleMutant.js
+
+plugin.fixChinaOffset.isInGoogle = (function () { // insane_is_in_china
+  // This set of points roughly illustrates the scope of Google's
+  // distortion. It has nothing to do with national borders etc.
+  // Points around Hong Kong/Shenzhen are mapped with a little more precision,
+  // in hope that it will make agents work a bit more smoothly there.
+  //
+  // Edits around these points are welcome.
+  var POINTS = [
+    // start hkmo
+    114.433722, 22.064310,
+    114.009458, 22.182105,
+    113.599275, 22.121763,
+    113.583463, 22.176002,
+    113.530900, 22.175318,
+    113.529542, 22.210608,
+    113.613377, 22.227435,
+    113.938514, 22.483714,
+    114.043449, 22.500274,
+    114.138506, 22.550640,
+    114.222984, 22.550960,
+    114.366803, 22.524255,
+    // end hkmo
+    115.254019, 20.235733,
+    121.456316, 26.504442,
+    123.417261, 30.355685,
+    124.289197, 39.761103,
+    126.880509, 41.774504,
+    127.887261, 41.370015,
+    128.214602, 41.965359,
+    129.698745, 42.452788,
+    130.766139, 42.668534,
+    131.282487, 45.037051,
+    133.142361, 44.842986,
+    134.882453, 48.370596,
+    132.235531, 47.785403,
+    130.980075, 47.804860,
+    130.659026, 48.968383,
+    127.860252, 50.043973,
+    125.284310, 53.667091,
+    120.619316, 53.100485,
+    119.403751, 50.105903,
+    117.070862, 49.690388,
+    115.586019, 47.995542,
+    118.599613, 47.927785,
+    118.260771, 46.707335,
+    113.534759, 44.735134,
+    112.093739, 45.001999,
+    111.431259, 43.489381,
+    105.206324, 41.809510,
+    96.485703, 42.778692,
+    94.167961, 44.991668,
+    91.130430, 45.192938,
+    90.694601, 47.754437,
+    87.356293, 49.232005,
+    85.375791, 48.263928,
+    85.876055, 47.109272,
+    82.935423, 47.285727,
+    81.929808, 45.506317,
+    79.919457, 45.108122,
+    79.841455, 42.178752,
+    73.334917, 40.076332,
+    73.241805, 39.062331,
+    79.031902, 34.206413,
+    78.738395, 31.578004,
+    80.715812, 30.453822,
+    81.821692, 30.585965,
+    85.501663, 28.208463,
+    92.096061, 27.754241,
+    94.699781, 29.357171,
+    96.079442, 29.429559,
+    98.910308, 27.140660,
+    97.404057, 24.494701,
+    99.400021, 23.168966,
+    100.697449, 21.475914,
+    102.976870, 22.616482,
+    105.476997, 23.244292,
+    108.565621, 20.907735,
+    107.730505, 18.193406,
+    110.669856, 17.754550,
+  ];
+  var lats = POINTS.filter(function (_, idx) { return idx % 2 === 1; });
+  var lngs = POINTS.filter(function (_, idx) { return idx % 2 === 0; });
+  POINTS = null; // not needed anyway...
+
+  /// *** pnpoly *** ///
+  // Wm. Franklin's 8-line point-in-polygon C program
+  // Copyright (c) 1970-2003, Wm. Randolph Franklin
+  // Copyright (c) 2017, Mingye Wang (js translation)
+  //
+  // Permission is hereby granted, free of charge, to any person obtaining
+  // a copy of this software and associated documentation files (the
+  // "Software"), to deal in the Software without restriction, including
+  // without limitation the rights to use, copy, modify, merge, publish,
+  // distribute, sublicense, and/or sell copies of the Software, and to
+  // permit persons to whom the Software is furnished to do so, subject to
+  // the following conditions:
+  //
+  //   1. Redistributions of source code must retain the above copyright
+  //      notice, this list of conditions and the following disclaimers.
+  //   2. Redistributions in binary form must reproduce the above
+  //      copyright notice in the documentation and/or other materials
+  //      provided with the distribution.
+  //   3. The name of W. Randolph Franklin may not be used to endorse or
+  //      promote products derived from this Software without specific
+  //      prior written permission.
+  //
+  // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+  // EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+  // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+  // NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+  // LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+  // OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+  // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+  var pnpoly = function (xs, ys, x, y) {
+    if (!(xs.length === ys.length)) { throw new Error('pnpoly: assert(xs.length === ys.length)'); }
+    var inside = 0;
+    for (var i = 0, j = xs.length - 1; i < xs.length; j = i++) {
+      inside ^= ys[i] > y !== ys[j] > y &&
+                x < (xs[j] - xs[i]) * (y - ys[i]) / (ys[j] - ys[i]) + xs[i];
+    }
+    return !!inside;
+  };
+  /// ^^^ pnpoly ^^^ ///
+
+  var isInGoogle = function (coords) {
+    // Yank out South China Sea as it's not distorted.
+    return coords.lat >= 17.754 && coords.lat <= 55.8271 &&
+           coords.lng >= 72.004 && coords.lng <= 137.8347 &&
+           pnpoly(lats, lngs, coords.lat, coords.lng);
+  };
+
+  return isInGoogle;
+})();
+
+plugin.fixChinaOffset.gcjObfs = (function () {
+  /// Krasovsky 1940 ellipsoid
+  /// @const
+  var GCJ_A = 6378245;
+  var GCJ_EE = 0.00669342162296594323; // f = 1/298.3; e^2 = 2*f - f**2
+
+  var gcjObfs = function (wgs) {
+
+    var x = wgs.lng - 105,
+      y = wgs.lat - 35;
+    // These distortion functions accept (x = lon - 105, y = lat - 35).
+    // They return distortions in terms of arc lengths, in meters.
+    var dLat_m = -100 + 2 * x + 3 * y + 0.2 * y * y + 0.1 * x * y + 0.2 * Math.sqrt(Math.abs(x)) +
+      20 / 3 * (
+        2 * Math.sin(x * 6 * Math.PI) + 2 * Math.sin(x * 2 * Math.PI) +
+        2 * Math.sin(y * Math.PI) + 4 * Math.sin(y / 3 * Math.PI) +
+        16 * Math.sin(y / 12 * Math.PI) + 32 * Math.sin(y / 30 * Math.PI));
+    var dLon_m = 300 + x + 2 * y + 0.1 * x * x + 0.1 * x * y + 0.1 * Math.sqrt(Math.abs(x)) +
+      20 / 3 * (
+        2 * Math.sin(x * 6 * Math.PI) + 2 * Math.sin(x * 2 * Math.PI) +
+        2 * Math.sin(x * Math.PI) + 4 * Math.sin(x / 3 * Math.PI) +
+        15 * Math.sin(x / 12 * Math.PI) + 30 * Math.sin(x / 30 * Math.PI));
+
+    var radLat = wgs.lat / 180 * Math.PI;
+    var magic = 1 - GCJ_EE * Math.pow(Math.sin(radLat), 2); // just a common expr
+
+    // Arc lengths per degree, on the wrong ellipsoid
+    var lat_deg_arclen = Math.PI / 180 * (GCJ_A * (1 - GCJ_EE)) * Math.pow(magic, 1.5);
+    var lon_deg_arclen = Math.PI / 180 * (GCJ_A * Math.cos(radLat) / Math.sqrt(magic));
+
+    return {
+      lat: wgs.lat + dLat_m / lat_deg_arclen,
+      lng: wgs.lng + dLon_m / lon_deg_arclen,
+    };
+  };
+
+  return gcjObfs;
+})();
+
+plugin.fixChinaOffset.process = function (wgs) {
+  return plugin.fixChinaOffset.isInGoogle(wgs)
+    ? plugin.fixChinaOffset.gcjObfs(wgs)
+    : wgs;
+};
+
+///////// begin overwrited L.GridLayer /////////
+
+L.GridLayer.prototype._getTiledPixelBounds = (function () {
+  return function (center) {
+  /// modified here ///
+    center = window.plugin.fixChinaOffset.getLatLng(center, this.options);
+    /////////////////////
+    var map = this._map,
+      mapZoom = map._animatingZoom ? Math.max(map._animateToZoom, map.getZoom()) : map.getZoom(),
+      scale = map.getZoomScale(mapZoom, this._tileZoom),
+      pixelCenter = map.project(center, this._tileZoom).floor(),
+      halfSize = map.getSize().divideBy(scale * 2);
+
+    return new L.Bounds(pixelCenter.subtract(halfSize), pixelCenter.add(halfSize));
+  };
+})(L.GridLayer.prototype._getTiledPixelBounds);
+
+L.GridLayer.prototype._setZoomTransform = (function (original) {
+  return function (level, center, zoom) {
+    center = window.plugin.fixChinaOffset.getLatLng(center, this.options);
+    original.apply(this, [level, center, zoom]);
+  };
+})(L.GridLayer.prototype._setZoomTransform);
+
+L.GridLayer.GoogleMutant.prototype._update = (function (original) {
+  return function () {
+    this.options.needFixChinaOffset = true;
+    // zoom level check needs to happen before super's implementation (tile addition/creation)
+    // otherwise tiles may be missed if maxNativeZoom is not yet correctly determined
+    if (this._mutant) {
+      var center = this._map.getCenter();
+      /// modified here ///
+      center = window.plugin.fixChinaOffset.getLatLng(center, this.options);
+      /////////////////////
+      var _center = new google.maps.LatLng(center.lat, center.lng);
+
+      this._mutant.setCenter(_center);
+      var zoom = this._map.getZoom();
+      var fractionalLevel = zoom !== Math.round(zoom);
+      var mutantZoom = this._mutant.getZoom();
+
+      //ignore fractional zoom levels
+      if (!fractionalLevel && (zoom != mutantZoom)) {
+        this._mutant.setZoom(zoom);
+
+        if (this._mutantIsReady) this._checkZoomLevels();
+        //else zoom level check will be done later by 'idle' handler
+      }
+    }
+
+    L.GridLayer.prototype._update.call(this);
+  };
+})(L.GridLayer.GoogleMutant.prototype._update);
+
+window.plugin.fixChinaOffset.getLatLng = function (pos, options) {
+  // No offsets in satellite and hybrid maps
+  if (options.needFixChinaOffset === true && options.type !== 'satellite' && options.type !== 'hybrid') {
+    return plugin.fixChinaOffset.process(pos);
+  }
+  return pos;
+};
+
+var setup = function () {};
+
+// PLUGIN END //////////////////////////////////////////////////////////
+
+@@PLUGINEND@@