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L.Graticule.js

@@ -0,0 +1,104 @@
+/*
+ Graticule plugin for Leaflet powered maps.
+*/
+L.Graticule = L.GeoJSON.extend({
+
+    options: {
+        style: {
+            color: '#333',
+            weight: 1
+        },
+        interval: 20
+    },
+
+    initialize: function (options) {
+        L.Util.setOptions(this, options);
+        this._layers = {};
+
+        if (this.options.sphere) {
+            this.addData(this._getFrame());
+        } else {
+            this.addData(this._getGraticule());
+        }
+    },
+
+    _getFrame: function() {
+        return { "type": "Polygon",
+          "coordinates": [
+              this._getMeridian(-180).concat(this._getMeridian(180).reverse())
+          ]
+        };
+    },
+
+    _getGraticule: function () {
+        var features = [], interval = this.options.interval;
+
+        // Meridians
+        for (var lng = 0; lng <= 180; lng = lng + interval) {
+            features.push(this._getFeature(this._getMeridian(lng), {
+                "name": (lng) ? lng.toString() + "° E" : "Prime meridian"
+            }));
+            if (lng !== 0) {
+                features.push(this._getFeature(this._getMeridian(-lng), {
+                    "name": lng.toString() + "° W"
+                }));
+            }
+        }
+
+        // Parallels
+        for (var lat = 0; lat < 90; lat = lat + interval) {
+            features.push(this._getFeature(this._getParallel(lat), {
+                "name": (lat) ? lat.toString() + "° N" : "Equator"
+            }));
+            if (lat !== 0) {
+                features.push(this._getFeature(this._getParallel(-lat), {
+                    "name": lat.toString() + "° S"
+                }));
+            }
+        }
+
+        return {
+            "type": "FeatureCollection",
+            "features": features
+        };
+    },
+
+    _getMeridian: function (lng) {
+        lng = this._lngFix(lng);
+        var coords = [];
+        for (var lat = -90; lat <= 90; lat++) {
+            coords.push([lng, lat]);
+        }
+        return coords;
+    },
+
+    _getParallel: function (lat) {
+        var coords = [];
+        for (var lng = -180; lng <= 180; lng++) {
+            coords.push([this._lngFix(lng), lat]);
+        }
+        return coords;
+    },
+
+    _getFeature: function (coords, prop) {
+        return {
+            "type": "Feature",
+            "geometry": {
+                "type": "LineString",
+                "coordinates": coords
+            },
+            "properties": prop
+        };
+    },
+
+    _lngFix: function (lng) {
+        if (lng >= 180) return 179.999999;
+        if (lng <= -180) return -179.999999;
+        return lng;
+    }
+
+});
+
+L.graticule = function (options) {
+    return new L.Graticule(options);
+};