Polyline.encoded.js

/*
 * Utility functions to decode/encode numbers and array's of numbers
 * to/from strings (Google maps polyline encoding)
 *
 * Extends the L.Polyline and L.Polygon object with methods to convert
 * to and create from these strings.
 *
 * Jan Pieter Waagmeester <jieter@jieter.nl>
 *
 * Original code from:
 * http://facstaff.unca.edu/mcmcclur/GoogleMaps/EncodePolyline/
 * (which is down as of december 2014)
 */

(function () {
    'use strict';

    var defaultOptions = function (options) {
        if (typeof options === 'number') {
            // Legacy
            options = {
                precision: options
            };
        } else {
            options = options || {};
        }

        options.precision = options.precision || 5;
        options.factor = options.factor || Math.pow(10, options.precision);
        options.dimension = options.dimension || 2;
        return options;
    };

    var PolylineUtil = {
        encode: function (points, options) {
            options = defaultOptions(options);

            var flatPoints = [];
            for (var i = 0, len = points.length; i < len; ++i) {
                var point = points[i];

                if (options.dimension === 2) {
                    flatPoints.push(point.lat || point[0]);
                    flatPoints.push(point.lng || point[1]);
                } else {
                    for (var dim = 0; dim < options.dimension; ++dim) {
                        flatPoints.push(point[dim]);
                    }
                }
            }

            return this.encodeDeltas(flatPoints, options);
        },

        decode: function (encoded, options) {
            options = defaultOptions(options);

            var flatPoints = this.decodeDeltas(encoded, options);

            var points = [];
            for (var i = 0, len = flatPoints.length; i + (options.dimension - 1) < len;) {
                var point = [];

                for (var dim = 0; dim < options.dimension; ++dim) {
                    point.push(flatPoints[i++]);
                }

                points.push(point);
            }

            return points;
        },

        encodeDeltas: function (numbers, options) {
            options = defaultOptions(options);

            var lastNumbers = [];

            for (var i = 0, len = numbers.length; i < len;) {
                for (var d = 0; d < options.dimension; ++d, ++i) {
                    var num = numbers[i];
                    var delta = num - (lastNumbers[d] || 0);
                    lastNumbers[d] = num;

                    numbers[i] = delta;
                }
            }

            return this.encodeFloats(numbers, options);
        },

        decodeDeltas: function (encoded, options) {
            options = defaultOptions(options);

            var lastNumbers = [];

            var numbers = this.decodeFloats(encoded, options);
            for (var i = 0, len = numbers.length; i < len;) {
                for (var d = 0; d < options.dimension; ++d, ++i) {
                    numbers[i] = Math.round((lastNumbers[d] = numbers[i] + (lastNumbers[d] || 0)) * options.factor) / options.factor;
                }
            }

            return numbers;
        },

        encodeFloats: function (numbers, options) {
            options = defaultOptions(options);

            for (var i = 0, len = numbers.length; i < len; ++i) {
                numbers[i] = Math.round(numbers[i] * options.factor);
            }

            return this.encodeSignedIntegers(numbers);
        },

        decodeFloats: function (encoded, options) {
            options = defaultOptions(options);

            var numbers = this.decodeSignedIntegers(encoded);
            for (var i = 0, len = numbers.length; i < len; ++i) {
                numbers[i] /= options.factor;
            }

            return numbers;
        },

        encodeSignedIntegers: function (numbers) {
            for (var i = 0, len = numbers.length; i < len; ++i) {
                var num = numbers[i];
                numbers[i] = (num < 0) ? ~(num << 1) : (num << 1);
            }

            return this.encodeUnsignedIntegers(numbers);
        },

        decodeSignedIntegers: function (encoded) {
            var numbers = this.decodeUnsignedIntegers(encoded);

            for (var i = 0, len = numbers.length; i < len; ++i) {
                var num = numbers[i];
                numbers[i] = (num & 1) ? ~(num >> 1) : (num >> 1);
            }

            return numbers;
        },

        encodeUnsignedIntegers: function (numbers) {
            var encoded = '';
            for (var i = 0, len = numbers.length; i < len; ++i) {
                encoded += this.encodeUnsignedInteger(numbers[i]);
            }
            return encoded;
        },

        decodeUnsignedIntegers: function (encoded) {
            var numbers = [];

            var current = 0;
            var shift = 0;

            for (var i = 0, len = encoded.length; i < len; ++i) {
                var b = encoded.charCodeAt(i) - 63;

                current |= (b & 0x1f) << shift;

                if (b < 0x20) {
                    numbers.push(current);
                    current = 0;
                    shift = 0;
                } else {
                    shift += 5;
                }
            }

            return numbers;
        },

        encodeSignedInteger: function (num) {
            num = (num < 0) ? ~(num << 1) : (num << 1);
            return this.encodeUnsignedInteger(num);
        },

        // This function is very similar to Google's, but I added
        // some stuff to deal with the double slash issue.
        encodeUnsignedInteger: function (num) {
            var value, encoded = '';
            while (num >= 0x20) {
                value = (0x20 | (num & 0x1f)) + 63;
                encoded += (String.fromCharCode(value));
                num >>= 5;
            }
            value = num + 63;
            encoded += (String.fromCharCode(value));

            return encoded;
        }
    };

    // Export Node module
    if (typeof module === 'object' && typeof module.exports === 'object') {
        module.exports = PolylineUtil;
    }

    // Inject functionality into Leaflet
    if (typeof L === 'object') {
        if (!(L.Polyline.prototype.fromEncoded)) {
            L.Polyline.fromEncoded = function (encoded, options) {
                return L.polyline(PolylineUtil.decode(encoded), options);
            };
        }
        if (!(L.Polygon.prototype.fromEncoded)) {
            L.Polygon.fromEncoded = function (encoded, options) {
                return L.polygon(PolylineUtil.decode(encoded), options);
            };
        }

        var encodeMixin = {
            encodePath: function () {
                return PolylineUtil.encode(this.getLatLngs());
            }
        };

        if (!L.Polyline.prototype.encodePath) {
            L.Polyline.include(encodeMixin);
        }
        if (!L.Polygon.prototype.encodePath) {
            L.Polygon.include(encodeMixin);
        }

        L.PolylineUtil = PolylineUtil;
    }
})();