geojson-rewind.js

!function(e){"object"==typeof exports?module.exports=e():"function"==typeof define&&define.amd?define(e):"undefined"!=typeof window?window.geojsonRewind=e():"undefined"!=typeof global?global.geojsonRewind=e():"undefined"!=typeof self&&(self.geojsonRewind=e())}(function(){var define,module,exports;return (function e(t,n,r){function s(o,u){if(!n[o]){if(!t[o]){var a=typeof require=="function"&&require;if(!u&&a)return a(o,!0);if(i)return i(o,!0);throw new Error("Cannot find module '"+o+"'")}var f=n[o]={exports:{}};t[o][0].call(f.exports,function(e){var n=t[o][1][e];return s(n?n:e)},f,f.exports,e,t,n,r)}return n[o].exports}var i=typeof require=="function"&&require;for(var o=0;o<r.length;o++)s(r[o]);return s})({1:[function(require,module,exports){
var geojsonArea = require('geojson-area');

module.exports = rewind;

function rewind(gj, outer) {
    switch ((gj && gj.type) || null) {
        case 'FeatureCollection':
            gj.features = gj.features.map(curryOuter(rewind, outer));
            return gj;
        case 'Feature':
            gj.geometry = rewind(gj.geometry, outer);
            return gj;
        case 'Polygon':
        case 'MultiPolygon':
            return correct(gj, outer);
        default:
            return gj;
    }
}

function curryOuter(a, b) {
    return function(_) { return a(_, b); };
}

function correct(_, outer) {
    if (_.type === 'Polygon') {
        _.coordinates = correctRings(_.coordinates, outer);
    } else if (_.type === 'MultiPolygon') {
        _.coordinates = _.coordinates.map(curryOuter(correctRings, outer));
    }
    return _;
}

function correctRings(_, outer) {
    outer = !!outer;
    _[0] = wind(_[0], !outer);
    for (var i = 1; i < _.length; i++) {
        _[i] = wind(_[i], outer);
    }
    return _;
}

function wind(_, dir) {
    return cw(_) === dir ? _ : _.reverse();
}

function cw(_) {
    return geojsonArea.ring(_) >= 0;
}

},{"geojson-area":2}],2:[function(require,module,exports){
var wgs84 = require('wgs84');

module.exports.geometry = geometry;
module.exports.ring = ringArea;

function geometry(_) {
    if (_.type === 'Polygon') return polygonArea(_.coordinates);
    else if (_.type === 'MultiPolygon') {
        var area = 0;
        for (var i = 0; i < _.coordinates.length; i++) {
            area += polygonArea(_.coordinates[i]);
        }
        return area;
    } else {
        return null;
    }
}

function polygonArea(coords) {
    var area = 0;
    if (coords && coords.length > 0) {
        area += Math.abs(ringArea(coords[0]));
        for (var i = 1; i < coords.length; i++) {
            area -= Math.abs(ringArea(coords[i]));
        }
    }
    return area;
}

/**
 * Calculate the approximate area of the polygon were it projected onto
 *     the earth.  Note that this area will be positive if ring is oriented
 *     clockwise, otherwise it will be negative.
 *
 * Reference:
 * Robert. G. Chamberlain and William H. Duquette, "Some Algorithms for
 *     Polygons on a Sphere", JPL Publication 07-03, Jet Propulsion
 *     Laboratory, Pasadena, CA, June 2007 http://trs-new.jpl.nasa.gov/dspace/handle/2014/40409
 *
 * Returns:
 * {float} The approximate signed geodesic area of the polygon in square
 *     meters.
 */

function ringArea(coords) {
    var area = 0;

    if (coords.length > 2) {
        var p1, p2;
        for (var i = 0; i < coords.length - 1; i++) {
            p1 = coords[i];
            p2 = coords[i + 1];
            area += rad(p2[0] - p1[0]) * (2 + Math.sin(rad(p1[1])) + Math.sin(rad(p2[1])));
        }

        area = area * wgs84.RADIUS * wgs84.RADIUS / 2;
    }

    return area;
}

function rad(_) {
    return _ * Math.PI / 180;
}

},{"wgs84":3}],3:[function(require,module,exports){
module.exports.RADIUS = 6378137;
module.exports.FLATTENING = 1/298.257223563;
module.exports.POLAR_RADIUS = 6356752.3142;},{}]},{},[1])
(1)
});
;