ADD support for encoded path

docs/endpoints.rst

@@ -35,7 +35,9 @@ Static images
 
     * e.g. ``5.9,45.8|5.9,47.8|10.5,47.8|10.5,45.8|5.9,45.8``
 
-  * ``latlng`` - indicates the ``path`` coordinates are in ``lat,lng`` order rather than the usual ``lng,lat``
+  * ``encodedpath`` - an alternative way to provide a path using Google's polyline encoding. Only used if ``path`` is not provided.
+    * more details: https://developers.google.com/maps/documentation/utilities/polylinealgorithm
+  * ``latlng`` - indicates the ``path`` coordinates are in ``lat,lng`` order rather than the usual ``lng,lat``. possible values: ``true`` or ``1``
   * ``fill`` - color to use as the fill (e.g. ``red``, ``rgba(255,255,255,0.5)``, ``#0000ff``)
   * ``stroke`` - color of the path stroke
   * ``width`` - width of the stroke

src/serve_rendered.js

@@ -504,6 +504,11 @@ module.exports = function(options, repo, params, id, dataResolver) {
         path.push(pair);
       }
     });
+
+    if(path.length==0){
+      path = utils.decodePolyline(query.encodedpath);
+    }
+
     return path;
   };
 

src/utils.js

@@ -116,3 +116,57 @@ module.exports.getFontsPbf = function(allowedFonts, fontPath, names, range, fall
     }, reject);
   });
 };
+
+// From: https://github.com/mapbox/polyline/blob/master/src/polyline.js
+module.exports.decodePolyline = function(str, precision) {
+    var index = 0,
+        lat = 0,
+        lng = 0,
+        coordinates = [],
+        shift = 0,
+        result = 0,
+        byte = null,
+        latitude_change,
+        longitude_change,
+        factor = Math.pow(10, precision || 5);
+
+    if(str==null){
+      return [];
+    }
+
+    // Coordinates have variable length when encoded, so just keep
+    // track of whether we've hit the end of the string. In each
+    // loop iteration, a single coordinate is decoded.
+    while (index < str.length) {
+
+        // Reset shift, result, and byte
+        byte = null;
+        shift = 0;
+        result = 0;
+
+        do {
+            byte = str.charCodeAt(index++) - 63;
+            result |= (byte & 0x1f) << shift;
+            shift += 5;
+        } while (byte >= 0x20);
+
+        latitude_change = ((result & 1) ? ~(result >> 1) : (result >> 1));
+
+        shift = result = 0;
+
+        do {
+            byte = str.charCodeAt(index++) - 63;
+            result |= (byte & 0x1f) << shift;
+            shift += 5;
+        } while (byte >= 0x20);
+
+        longitude_change = ((result & 1) ? ~(result >> 1) : (result >> 1));
+
+        lat += latitude_change;
+        lng += longitude_change;
+
+        coordinates.push([lng / factor, lat / factor]);
+    }
+
+    return coordinates;
+};