New function to get the center of a tile

README.md

@@ -38,6 +38,7 @@ tileToQuadkey(tile) | get the quadkey for a tile
 quadkeyToTile(quadkey) | get the tile for a quadkey
 pointToTile(lon, lat, zoom) | get the tile for a point at a specified zoom level
 pointToTileFraction(lon, lat, zoom) | get the precise fractional tile location for a point at a zoom level
+tileToCenterPoint(tile) | Get the GeoJSON geometry of the center of the tile.
 
 ## tests
 

index.js

@@ -280,6 +280,29 @@ function pointToTileFraction(lon, lat, z) {
     return [x, y, z];
 }
 
+
+/**
+ * Get the center of a tile as Point GeoJSON
+ *
+ * @name tileToCenterPoint
+ * @param {Array<number>} bbox
+ * @returns {Feature<Point>}
+ * @example
+ * var point = tileToCenterPoint([0,0,10])
+ * //= point
+ */
+
+function tileToCenterPoint(tile) {
+    var bbox = tileToBBOX(tile)
+
+    return {type: 'Point',
+            coordinates: [
+                (bbox[0] + bbox[2]) / 2,
+                (bbox[1] + bbox[3]) / 2
+            ]
+          }
+}
+
 module.exports = {
     tileToGeoJSON: tileToGeoJSON,
     tileToBBOX: tileToBBOX,
@@ -293,5 +316,6 @@ module.exports = {
     quadkeyToTile: quadkeyToTile,
     pointToTile: pointToTile,
     bboxToTile: bboxToTile,
-    pointToTileFraction: pointToTileFraction
+    pointToTileFraction: pointToTileFraction,
+    tileToCenterPoint: tileToCenterPoint
 };

package.json

@@ -28,4 +28,4 @@
     "tap": "^1.3.4"
   },
   "dependencies": {}
-}
+}

test.js

@@ -214,3 +214,17 @@ test('pointToTile -- cross meridian', function (t) {
     t.deepEqual(tilebelt.bboxToTile([-0.000001, -85, 1000000, 85]), [0, 0, 0]);
     t.end();
 });
+
+test('tile to center point', function (t) {
+    var tile = tilebelt.pointToTile(0, 0, 10);
+    var center = tilebelt.tileToCenterPoint(tile)
+    t.deepEqual(center,
+      { type: 'Point', coordinates: [0.17578125, -0.17578014699614353]})
+
+    var center2 = tilebelt.tileToCenterPoint(tilebelt.quadkeyToTile('300000000000000'))
+    t.deepEqual(center2,
+      { type: 'Point', coordinates: [0.0054931640625, -0.005493164028840922]}
+    )
+
+    t.end();
+});