GlobalMercator Node Module

GlobalMapTiles.js

/*
 GlobalMapTiles - part of Aggregate Map Tools
 Version 1.0
 Copyright (c) 2009 The Bivings Group
 All rights reserved.
 Author: John Bafford

 http://www.bivings.com/
 http://bafford.com/softare/aggregate-map-tools/

 Based on GDAL2Tiles / globalmaptiles.py
 Original python version Copyright (c) 2008 Klokan Petr Pridal. All rights reserved.
 http://www.klokan.cz/projects/gdal2tiles/

 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:

 The above copyright notice and this permission notice shall be included
 in all copies or substantial portions of the Software.

 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.
 */

exports.GlobalMercator = function () {
    this.tileSize = 256;
    this.initialResolution = 2 * Math.PI * 6378137 / this.tileSize;
    this.originShift = 2 * Math.PI * 6378137 / 2.0;

    //Converts given lat/lon in WGS84 Datum to XY in Spherical Mercator EPSG:900913
    this.LatLonToMeters = function (lat, lon) {
        var mx = lon * this.originShift / 180.0;
        var my = Math.log(Math.tan((90 + lat) * Math.PI / 360.0)) / (Math.PI / 180.0);

        my *= this.originShift / 180.0;

        return [mx, my];
    };

    //Converts XY point from Spherical Mercator EPSG:900913 to lat/lon in WGS84 Datum
    this.MetersToLatLon = function (mx, my) {
        var lon = (mx / this.originShift) * 180.0;
        var lat = (my / this.originShift) * 180.0;

        lat = 180 / Math.PI * (2 * Math.atan(Math.exp(lat * Math.PI / 180.0)) - Math.PI / 2.0);

        return [lat, lon];
    };

    //Converts pixel coordinates in given zoom level of pyramid to EPSG:900913
    this.PixelsToMeters = function (px, py, zoom) {
        var res = this.Resolution(zoom);
        var mx = px * res - this.originShift;
        var my = py * res - this.originShift;

        return [mx, my];
    };

    //Converts EPSG:900913 to pyramid pixel coordinates in given zoom level
    this.MetersToPixels = function (mx, my, zoom) {
        var res = this.Resolution(zoom);

        var px = (mx + this.originShift) / res;
        var py = (my + this.originShift) / res;

        return [px, py];
    };

    //Returns a tile covering region in given pixel coordinates
    this.PixelsToTile = function (px, py, nonRound) {
        var tx;
        var ty;
        if (nonRound) {
            tx = (px / this.tileSize) - 1;
            ty = (py / this.tileSize) - 1;
        } else {
            tx = Math.ceil(px / this.tileSize) - 1;
            ty = Math.ceil(py / this.tileSize) - 1;

        }
        return [tx, ty];

    };

    //Returns tile for given mercator coordinates
    this.MetersToTile = function (mx, my, zoom, nonRound) {
        var p = this.MetersToPixels(mx, my, zoom);

        return this.PixelsToTile(p[0], p[1], nonRound);
    };

    //Returns bounds of the given tile in EPSG:900913 coordinates
    this.TileBounds = function (tx, ty, zoom) {
        var min = this.PixelsToMeters(tx * this.tileSize, ty * this.tileSize, zoom);
        var max = this.PixelsToMeters((tx + 1) * this.tileSize, (ty + 1) * this.tileSize, zoom);

        return [min[0], min[1], max[0], max[1]];
    };

    //Returns bounds of the given tile in latutude/longitude using WGS84 datum
    this.TileLatLonBounds = function (tx, ty, zoom) {
        var bounds = this.TileBounds(tx, ty, zoom);

        var min = this.MetersToLatLon(bounds[0], bounds[1]);
        var max = this.MetersToLatLon(bounds[2], bounds[3]);

        return [min[0], min[1], max[0], max[1]];
    };

    //Resolution (meters/pixel) for given zoom level (measured at Equator)
    this.Resolution = function (zoom) {
        return this.initialResolution / (1 << zoom);
    };

    //Converts TMS tile coordinates to Microsoft QuadTree
    this.QuadTree = function (tx, ty, zoom) {
        var quadtree = '';

        ty = ((1 << zoom) - 1) - ty;
        for (var i = zoom; i >= 1; i--) {
            var digit = 0;

            var mask = 1 << (i - 1);

            if ((tx & mask) != 0) {
                digit += 1;
            }

            if ((ty & mask) != 0) {
                digit += 2;
            }

            quadtree += digit;
        }

        return quadtree;
    };

    //Converts a quadtree to tile coordinates
    this.QuadTreeToTile = function (quadtree, zoom) {
        var tx = 0;
        var ty = 0;

        for (var i = zoom; i >= 1; i--) {
            var ch = quadtree[zoom - i];
            var mask = 1 << (i - 1);

            var digit = ch - '0';

            if (digit & 1) {
                tx += mask;
            }

            if (digit & 2) {
                ty += mask;
            }
        }

        ty = ((1 << zoom) - 1) - ty;

        return [tx, ty];
    };

    //Converts a latitude and longitude to quadtree at the specified zoom level
    this.LatLonToQuadTree = function (lat, lon, zoom) {
        var m = this.LatLonToMeters(lat, lon);
        var t = this.MetersToTile(m[0], m[1], zoom);

        return this.QuadTree(t[0], t[1], zoom);
    };

    //Converts a quadtree location into a latitude/longitude bounding rectangle
    this.QuadTreeToLatLon = function (quadtree) {
        var zoom = quadtree.length;

        var t = this.QuadTreeToTile(quadtree, zoom);

        return this.TileLatLonBounds(t[0], t[1], zoom);
    };

    this._getTileBounds = function (zoom, latLon, latLonMax, nonRound, callback) {
        var lat = latLon[0];
        var lon = latLon[1];
        var latMax, lonMax;

        if (latLonMax) {
            latMax = latLonMax[0];
            lonMax = latLonMax[1];

            if (latMax < lat || lonMax < lon) {
                return false;
            }
        }

        var m = this.LatLonToMeters(latLon[0], latLon[1]);
        var tmin = this.MetersToTile(m[0], m[1], zoom, nonRound);
        var tmax;

        if (latLonMax) {
            m = this.LatLonToMeters(latLonMax[0], latLonMax[1]);
            tmax = this.MetersToTile(m[0], m[1], zoom, nonRound);
        }
        else {
            tmax = tmin;
        }
        callback(tmin, tmax);
    };

    //Returns a list of all of the quadtree locations at a given zoom level within a latitude/longude box
    this.GetTileBounds = function (zoom, latLon, latLonMax, callback) {
        this._getTileBounds(zoom, latLon, latLonMax, false, function (tmin, tmax) {
            callback({
                x: {min: tmin[0], max: tmax[0]},
                y: {min: tmin[1], max: tmax[1]}
            });
        });
    };

    this.GetTileBoundsRaw = function (zoom, latLon, latLonMax, callback) {
        this._getTileBounds(zoom, latLon, latLonMax, true, function (tmin, tmax) {
            callback({
                x: {min: tmin[0], max: tmax[0]},
                y: {min: tmin[1], max: tmax[1]}
            });
        });
    };

    //Returns a list of all of the quadtree locations at a given zoom level within a latitude/longude box
    this.GetQuadTreeList = function (zoom, latLon, latLonMax) {
        this._getTileBounds(zoom, latLon, latLonMax, false, function (tmin, tmax) {
            var arr = {};
            for (var ty = tmin[1]; ty <= tmax[1]; ty++) {
                for (var tx = tmin[0]; tx <= tmax[0]; tx++) {
                    var quadtree = this.QuadTree(tx, ty, zoom);
                    arr[quadtree] = this.TileLatLonBounds(tx, ty, zoom);
                }
            }

            return arr;
        });
    }


};