node-red-contrib-snap4city-user/point-within-polygon.js

Nodes for Snap4city project, targeted to standard user (no developer)

/* NODE-RED-CONTRIB-SNAP4CITY-USER
   Copyright (C) 2018 DISIT Lab http://www.disit.org - University of Florence

   This program is free software: you can redistribute it and/or modify
   it under the terms of the GNU Affero General Public License as
   published by the Free Software Foundation, either version 3 of the
   License, or (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU Affero General Public License for more details.

   You should have received a copy of the GNU Affero General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>. */
module.exports = function (RED) {

    function PointWithinPolygon(config) {
        var wellknown = require("wellknown");

        RED.nodes.createNode(this, config);
        var node = this;
        node.on('input', function (msg) {
            var polygon = (msg.payload.polygon ? msg.payload.polygon : config.polygon);
            var pointlatitude = parseFloat(msg.payload.pointlatitude ? msg.payload.pointlatitude : config.pointlatitude);
            var pointlongitude = parseFloat(msg.payload.pointlongitude ? msg.payload.pointlongitude : config.pointlongitude);
            geoJSONPolygon = wellknown.parse(polygon);
            msg.payload = inside([pointlongitude, pointlatitude], geoJSONPolygon.coordinates[0]);
            node.send(msg);
        });
    }

    function inside(point, vs) {
        // ray-casting algorithm based on
        // http://www.ecse.rpi.edu/Homepages/wrf/Research/Short_Notes/pnpoly.html

        var x = point[0],
            y = point[1];

        var inside = false;
        for (var i = 0, j = vs.length - 1; i < vs.length; j = i++) {
            var xi = vs[i][0],
                yi = vs[i][1];
            var xj = vs[j][0],
                yj = vs[j][1];

            var intersect = ((yi > y) != (yj > y)) &&
                (x < (xj - xi) * (y - yi) / (yj - yi) + xi);
            if (intersect) inside = !inside;
        }

        return inside;
    };


    RED.nodes.registerType("point-within-polygon", PointWithinPolygon);

    RED.httpAdmin.get('/s4c/js/*', function (req, res) {
        var options = {
            root: __dirname + '/lib/js/',
            dotfiles: 'deny'
        };

        res.sendFile(req.params[0], options);
    });

    RED.httpAdmin.get('/s4c/css/*', function (req, res) {
        var options = {
            root: __dirname + '/lib/css/',
            dotfiles: 'deny'
        };

        res.sendFile(req.params[0], options);
    });

}