@turf/buffer attempt to replace jsts

packages/turf-buffer/bench.js

@@ -16,6 +16,7 @@ const fixtures = fs.readdirSync(directory).map(filename => {
 /**
  * Benchmark Results
  *
+ * ==before==
  * 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)
@@ -24,6 +25,16 @@ const fixtures = fs.readdirSync(directory).map(filename => {
  * 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)
+ *
+ * ==after==
+ * feature-collection-points x 6,198 ops/sec ±13.12% (58 runs sampled)
+ * geometry-collection-points x 6,518 ops/sec ±13.37% (67 runs sampled)
+ * linestring x 1,694 ops/sec ±4.85% (71 runs sampled)
+ * multi-linestring x 466 ops/sec ±4.26% (77 runs sampled)
+ * multi-point x 12,055 ops/sec ±5.63% (77 runs sampled)
+ * multi-polygon x 202 ops/sec ±1.73% (83 runs sampled)
+ * point x 43,109 ops/sec ±1.58% (89 runs sampled)
+ * polygon-with-holes x 438 ops/sec ±1.70% (86 runs sampled)
  */
 const suite = new Benchmark.Suite('turf-buffer');
 for (const {name, geojson} of fixtures) {

packages/turf-buffer/index.js

@@ -1,59 +1,103 @@
-// 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 Offset = require('polygon-offset');
+var circle = require('@turf/circle');
+var getCoords = require('@turf/invariant').getCoords;
+var meta = require('@turf/meta');
+var featureEach = meta.featureEach;
+var geomEach = meta.geomEach;
 var helpers = require('@turf/helpers');
 var featureCollection = helpers.featureCollection;
-var jsts = require('jsts');
-var normalize = require('@mapbox/geojson-normalize');
+var point = helpers.point;
+var multiPolygon = helpers.multiPolygon;
+var polygon = helpers.polygon;
+var distanceToDegrees = helpers.distanceToDegrees;
 
 /**
  * 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>} geojson 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
- * @addToMap pt, buffered
+ * @param {string} [units='kilometers'] any of the options supported by turf units
+ * @param {number} [padding=10] determines the offset padding
+ * @param {number} [steps=64] number of steps
+ * @returns {FeatureCollection|Feature<Polygon|MultiPolygon>} buffered features
  * @example
- * var pt = {
+ * var point = {
  *   "type": "Feature",
  *   "properties": {},
  *   "geometry": {
  *     "type": "Point",
- *     "coordinates": [-90.548630, 14.616599]
+ *     "coordinates": [-110, 15]
  *   }
  * };
- * var unit = 'miles';
  *
- * var buffered = turf.buffer(pt, 500, unit);
+ * var buffered = turf.buffer(point, 500, 'miles');
  *
- * //=buffered
+ * //addToMap
+ * var addToMap = [point, buffered];
  */
+module.exports = function (geojson, radius, units, padding, steps) {
+    // validation
+    if (radius === undefined || radius === null) throw new Error('radius is required');
 
-module.exports = function (feature, radius, units) {
-
-    var degrees = helpers.distanceToDegrees(radius, units);
-    var fc = normalize(feature);
-    var buffered = normalize(featureCollection(fc.features.map(function (f) {
-        return bufferOp(f, degrees);
-    })));
+    // default params
+    padding = padding || 10;
+    steps = steps || 64;
 
-    if (buffered.features.length > 1) return buffered;
-    else if (buffered.features.length === 1) return buffered.features[0];
+    var results = [];
+    switch (geojson.type) {
+    case 'GeometryCollection':
+        geomEach(geojson, function (feature) {
+            results.push(buffer(feature, radius, units, padding));
+        });
+        break;
+    case 'FeatureCollection':
+        featureEach(geojson, function (feature) {
+            results.push(buffer(feature, radius, units, padding));
+        });
+        break;
+    default:
+        return buffer(geojson, radius, units, padding);
+    }
+    return featureCollection(results);
 };
 
-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} [padding=10] determines the offset padding
+ * @param {number} [steps=64] number of steps
+ * @returns {Feature<Polygon|MultiPolygon>} buffered feature
+ */
+function buffer(feature, radius, units, padding, steps) {
+    var geom = (feature.geometry) ? feature.geometry.type : feature.type;
+    var coords = getCoords(feature);
+    var properties = feature.properties || {};
+    var offset = new Offset();
+    var distance = distanceToDegrees(radius, units);
 
-    return {
-        type: 'Feature',
-        geometry: buffered,
-        properties: {}
-    };
+    switch (geom) {
+    case 'Point':
+        var buffered = circle(coords, radius, steps, units);
+        buffered.properties = properties;
+        return buffered;
+    case 'MultiPoint':
+        var buffers = [];
+        coords.forEach(function (coord) {
+            buffers.push(getCoords(circle(point(coord, properties), radius, steps, units)));
+        });
+        return multiPolygon(buffers, properties);
+    case 'LineString':
+    case 'MultiLineString':
+        var line = offset.data(coords).offsetLine(distance);
+        return polygon(line, properties);
+    case 'Polygon':
+    case 'MultiPolygon':
+        var poly = offset.data(coords).margin(distance);
+        return polygon(poly, properties);
+    }
 }

packages/turf-buffer/package.json

@@ -39,9 +39,10 @@
     "write-json-file": "^2.0.0"
   },
   "dependencies": {
-    "@mapbox/geojson-normalize": "0.0.1",
-    "@turf/combine": "^4.1.0",
-    "@turf/helpers": "^4.1.0",
-    "jsts": "1.3.0"
+    "@turf/circle": "^4.0.1",
+    "@turf/helpers": "^4.0.1",
+    "@turf/invariant": "^4.0.1",
+    "@turf/meta": "^4.0.2",
+    "polygon-offset": "^0.3.1"
   }
 }