buffer units other than degrees #283

packages/turf-buffer/bench.js

@@ -16,14 +16,15 @@ const fixtures = fs.readdirSync(directory).map(filename => {
 /**
  * Benchmark Results
  *
- * feature-collection-points x 3,792 ops/sec ±10.41% (82 runs sampled)
- * geometry-collection-points x 4,346 ops/sec ±2.05% (90 runs sampled)
- * linestring x 9,087 ops/sec ±2.14% (89 runs sampled)
- * multi-linestring x 1,145 ops/sec ±9.46% (80 runs sampled)
- * multi-point x 4,898 ops/sec ±4.73% (78 runs sampled)
- * multi-polygon x 1,737 ops/sec ±9.31% (66 runs sampled)
- * point x 11,907 ops/sec ±8.10% (72 runs sampled)
- * polygon-with-holes x 6,417 ops/sec ±6.16% (79 runs sampled)
+ * feature-collection-points x 9,335 ops/sec ±1.37% (88 runs sampled)
+ * geometry-collection-points x 9,505 ops/sec ±1.57% (86 runs sampled)
+ * linestring x 7,977 ops/sec ±17.93% (75 runs sampled)
+ * multi-linestring x 1,371 ops/sec ±2.00% (88 runs sampled)
+ * multi-point x 515 ops/sec ±3.35% (85 runs sampled)
+ * multi-polygon x 2,549 ops/sec ±3.03% (88 runs sampled)
+ * north-latitude-points x 812 ops/sec ±2.31% (88 runs sampled)
+ * point x 42,867 ops/sec ±1.38% (89 runs sampled)
+ * polygon-with-holes x 7,397 ops/sec ±1.93% (88 runs sampled)
  */
 const suite = new Benchmark.Suite('turf-buffer');
 for (const {name, geojson} of fixtures) {

packages/turf-buffer/index.js

@@ -1,22 +1,25 @@
-// http://stackoverflow.com/questions/839899/how-do-i-calculate-a-point-on-a-circles-circumference
-// radians = degrees * (pi/180)
-// https://github.com/bjornharrtell/jsts/blob/master/examples/buffer.html
-
+var jsts = require('jsts');
 var helpers = require('@turf/helpers');
+var circle = require('@turf/circle');
+var dissolve = require('@turf/dissolve');
+var meta = require('@turf/meta');
+var coordEach = meta.coordEach;
+var featureEach = meta.featureEach;
 var featureCollection = helpers.featureCollection;
-var jsts = require('jsts');
-var normalize = require('@mapbox/geojson-normalize');
+var distanceToDegrees = helpers.distanceToDegrees;
+var point = helpers.point;
 
 /**
  * Calculates a buffer for input features for a given radius. Units supported are miles, kilometers, and degrees.
  *
  * @name buffer
- * @param {(Feature|FeatureCollection)} feature input to be buffered
+ * @param {FeatureCollection|Feature<any>} feature input to be buffered
  * @param {number} radius distance to draw the buffer
- * @param {string} units any of the options supported by turf units
- * @return {FeatureCollection<Polygon>|FeatureCollection<MultiPolygon>|Polygon|MultiPolygon} buffered features
+ * @param {string} [units=kilometers] any of the options supported by turf units
+ * @param {number} [steps=64] number of steps
+ * @return {FeatureCollection|Feature<Polygon|MultiPolygon>} buffered features
  * @example
- * var pt = {
+ * var point = {
  *   "type": "Feature",
  *   "properties": {},
  *   "geometry": {
@@ -26,33 +29,67 @@ var normalize = require('@mapbox/geojson-normalize');
  * };
  * var unit = 'miles';
  *
- * var buffered = turf.buffer(pt, 500, unit);
+ * var buffered = turf.buffer(point, 500, unit);
+ *
  * //addToMap
- * var addToMap = [pt, buffered]
+ * var addToMap = [point, buffered]
  */
 
-module.exports = function (feature, radius, units) {
+module.exports = function (geojson, radius, units, steps) {
+    if (radius === undefined || radius === null) throw new Error('radius is required');
+    steps = steps || 64;
 
-    var degrees = helpers.distanceToDegrees(radius, units);
-    var fc = normalize(feature);
-    var buffered = normalize(featureCollection(fc.features.map(function (f) {
-        return bufferOp(f, degrees);
-    })));
+    switch (geojson.type) {
+    case 'GeometryCollection':
+    case 'FeatureCollection':
+        var results = [];
+        var features = (geojson.features) ? geojson.features : geojson.geometries || [];
 
-    if (buffered.features.length > 1) return buffered;
-    else if (buffered.features.length === 1) return buffered.features[0];
+        features.forEach(function (feature) {
+            featureEach(buffer(feature, radius, units, steps), function (buffered) {
+                results.push(buffered);
+            });
+        });
+        return featureCollection(results);
+    }
+    return buffer(geojson, radius, units, steps);
 };
 
-function bufferOp(feature, radius) {
-    var reader = new jsts.io.GeoJSONReader();
-    var geom = reader.read(feature.geometry);
-    var buffered = geom.buffer(radius);
-    var writer = new jsts.io.GeoJSONWriter();
-    buffered = writer.write(buffered);
+/**
+ * Buffer single Feature
+ *
+ * @private
+ * @param {Feature<any>} feature input to be buffered
+ * @param {number} radius distance to draw the buffer
+ * @param {string} [units='kilometers'] any of the options supported by turf units
+ * @param {number} [steps=64] number of steps
+ * @returns {Feature<Polygon|MultiPolygon>} buffered feature
+ */
+function buffer(feature, radius, units, steps) {
+    var properties = feature.properties || {};
+    var distance = distanceToDegrees(radius, units);
+    var geometry = (feature.type === 'Feature') ? feature.geometry : feature;
 
-    return {
-        type: 'Feature',
-        geometry: buffered,
-        properties: {}
-    };
+    switch (geometry.type) {
+    case 'Point':
+        return circle(feature, radius, steps, units);
+    case 'MultiPoint':
+        var polys = [];
+        coordEach(feature, function (coord) {
+            polys.push(circle(point(coord, properties), radius, steps, units));
+        });
+        return dissolve(featureCollection(polys));
+    case 'LineString':
+    case 'MultiLineString':
+    case 'Polygon':
+    case 'MultiPolygon':
+        var reader = new jsts.io.GeoJSONReader();
+        var geom = reader.read(geometry);
+        var buffered = geom.buffer(distance);
+        var writer = new jsts.io.GeoJSONWriter();
+        buffered = writer.write(buffered);
+        return helpers.feature(buffered, properties);
+    default:
+        throw new Error('geometry type ' + geometry.type + ' not supported');
+    }
 }

packages/turf-buffer/package.json

@@ -26,6 +26,10 @@
     "turf"
   ],
   "author": "Turf Authors",
+  "contributors": [
+    "Tom MacWright <@tmcw>",
+    "Denis Carriere <@DenisCarriere>"
+  ],
   "license": "MIT",
   "bugs": {
     "url": "https://github.com/Turfjs/turf/issues"
@@ -39,9 +43,10 @@
     "write-json-file": "^2.0.0"
   },
   "dependencies": {
-    "@mapbox/geojson-normalize": "0.0.1",
-    "@turf/combine": "^4.1.0",
+    "@turf/circle": "^4.1.0",
+    "@turf/dissolve": "^4.1.0",
     "@turf/helpers": "^4.1.0",
+    "@turf/meta": "^4.1.0",
     "jsts": "1.3.0"
   }
 }

packages/turf-buffer/test.js

@@ -4,6 +4,8 @@ const path = require('path');
 const load = require('load-json-file');
 const write = require('write-json-file');
 const truncate = require('@turf/truncate');
+const featureEach = require('@turf/meta').featureEach;
+const featureCollection = require('@turf/helpers').featureCollection;
 const buffer = require('./');
 
 const directories = {
@@ -25,7 +27,12 @@ test('turf-buffer', function (t) {
         radius = radius || 50;
         units = units || 'miles';
 
-        const results = truncate(buffer(geojson, radius, units, padding));
+        const buffered = truncate(buffer(geojson, radius, units, padding));
+
+        // Add Results to FeatureCollection
+        const results = featureCollection([]);
+        featureEach(buffered, feature => results.features.push(feature));
+        featureEach(geojson, feature => results.features.push(feature));
 
         if (process.env.REGEN) write.sync(directories.out + filename, results);
         t.deepEqual(results, load.sync(directories.out + filename), name);

packages/turf-buffer/test/in/feature-collection-points.geojson

@@ -3,9 +3,7 @@
   "features": [
     {
       "type": "Feature",
-      "properties": {
-        "foo": "bar"
-      },
+      "properties": {},
       "geometry": {
         "type": "MultiPoint",
         "coordinates": [

packages/turf-buffer/test/in/linestring.geojson

@@ -1,6 +1,8 @@
 {
   "type": "Feature",
-  "properties": {},
+  "properties": {
+    "foo": "bar"
+  },
   "geometry": {
     "type": "LineString",
     "coordinates": [

packages/turf-buffer/test/in/multi-point.geojson

@@ -1,6 +1,8 @@
 {
   "type": "Feature",
-  "properties": {},
+  "properties": {
+    "radius": 300
+  },
   "geometry": {
     "type": "MultiPoint",
     "coordinates": [

packages/turf-buffer/test/in/point.geojson

@@ -1,6 +1,8 @@
 {
   "type": "Feature",
-  "properties": {},
+  "properties": {
+    "foo": "bar"
+  },
   "geometry": {
     "type": "Point",
     "coordinates": [