Return geometry positions in a 512x512 tile

lib/vectortilefeature.js

@@ -38,7 +38,7 @@ function readTag(pbf, feature) {
 
 VectorTileFeature.types = ['Unknown', 'Point', 'LineString', 'Polygon'];
 
-VectorTileFeature.prototype.loadGeometry = function() {
+VectorTileFeature.prototype.loadGeometry = function(transformFunction) {
     var pbf = this._pbf;
     pbf.pos = this._geometry;
 
@@ -67,14 +67,14 @@ VectorTileFeature.prototype.loadGeometry = function() {
                 if (line) lines.push(line);
                 line = [];
             }
-
-            line.push(new Point(x, y));
+            line.push(transformFunction(x, y));
 
         } else if (cmd === 7) {
 
             // Workaround for https://github.com/mapbox/mapnik-vector-tile/issues/90
             if (line) {
-                line.push(line[0].clone()); // closePolygon
+                var firstLine = line[0].clone ? line[0].clone() : line[0].slice();
+                line.push(firstLine); // closePolygon
             }
 
         } else {
@@ -126,11 +126,16 @@ VectorTileFeature.prototype.bbox = function() {
     return [x1, y1, x2, y2];
 };
 
+
 VectorTileFeature.prototype.toGeoJSON = function(x, y, z) {
+    var transformFunction = function (x, y) {
+        return new Point(x, y);
+    };
+
     var size = this.extent * Math.pow(2, z),
         x0 = this.extent * x,
         y0 = this.extent * y,
-        coords = this.loadGeometry(),
+        coords = this.loadGeometry(transformFunction),
         type = VectorTileFeature.types[this.type],
         i, j;
 
@@ -192,6 +197,59 @@ VectorTileFeature.prototype.toGeoJSON = function(x, y, z) {
     return result;
 };
 
+VectorTileFeature.prototype.toTileCoordsJSON = function() {
+    // Resize tiles to 512x512 bounding box
+    var tileSize = 512;
+    var tileExtent = this.extent;
+    var transformFunction = function (x, y) {
+        return [
+            (x/tileExtent) * tileSize,
+            (y/tileExtent) * tileSize
+        ];
+    };
+
+    var type = VectorTileFeature.types[this.type];
+    var tileCoordsGeometry = this.loadGeometry(transformFunction);
+    var i;
+
+    switch (this.type) {
+        // Points
+        case 1:
+            var points = [];
+            for (i = 0; i < tileCoordsGeometry.length; i++) {
+                points[i] = tileCoordsGeometry[i][0];
+            }
+            tileCoordsGeometry = points;
+            break;
+
+        // Polygons
+        case 3:
+            tileCoordsGeometry = classifyRings(tileCoordsGeometry);
+            break;
+    }
+
+    if (tileCoordsGeometry.length === 1) {
+        tileCoordsGeometry = tileCoordsGeometry[0];
+    } else {
+        type = 'Multi' + type;
+    }
+
+    var jsonFeature = {
+        type: "Feature",
+        properties: this.properties,
+        geometry: {
+            type: type,
+            coordinates: tileCoordsGeometry
+        }
+    };
+
+    if ('id' in this) {
+        jsonFeature.id = this.id;
+    }
+
+    return jsonFeature;
+};
+
 // classifies an array of rings into polygons with outer rings and holes
 
 function classifyRings(rings) {