Implement circle (#187)

* done

* add test

* rename library turf_circle

lib/circle.dart

@@ -0,0 +1,4 @@
+library turf_circle;
+
+export 'package:geotypes/geotypes.dart';
+export 'src/circle.dart';

lib/src/circle.dart

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+import 'package:turf/helpers.dart';
+import 'package:turf/invariant.dart';
+import 'package:turf/src/booleans/boolean_helper.dart';
+import 'destination.dart';
+
+/// Takes a [Point] or a [Feature<Point>] and calculates the circle polygon given a radius in degrees, radians, miles, or kilometers; and steps for precision.
+///
+/// example:
+/// ```dart
+/// var properties = { 'foo': 'bar' };
+/// var point = Feature(geometry: Point(coordinates: Position.of([-75.343, 39.984])));
+/// final polygonCircle = circle(
+/// feature.geometry!,
+/// radius,
+/// steps: 32,
+/// unit: Unit.meters,
+/// properties: feature.properties,
+/// );
+/// ```
+Feature<Polygon> circle(
+ GeoJSONObject center,
+ num radius, {
+ num? steps,
+ Unit? unit,
+ Map<String, dynamic>? properties,
+}) {
+ steps ??= 64;
+ unit ??= Unit.kilometers;
+ Point origin;
+ final geometry = getGeom(center);
+ if (geometry is Point) {
+ origin = geometry;
+ } else {
+ throw GeometryNotSupported(geometry);
+ }
+ properties ??=
+ center is Feature && center.properties != null ? center.properties : {};
+ final List<Position> coordinates = [];
+ for (var i = 0; i < steps; i++) {
+ final c = destination(origin, radius, (i * -360) / steps, unit).coordinates;
+ coordinates.add(c);
+ }
+ coordinates.add(coordinates[0]);
+ return Feature<Polygon>(
+ properties: properties,
+ geometry: Polygon(coordinates: [coordinates]),
+ );
+}

test/components/circle_test.dart

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+import 'dart:convert';
+import 'dart:io';
+
+import 'package:test/test.dart';
+import 'package:turf/circle.dart';
+import 'package:turf/src/truncate.dart';
+import 'package:turf_equality/turf_equality.dart';
+
+import '../context/helper.dart';
+
+void main() {
+ group(
+ 'circle',
+ () {
+ test('circle -- add properties', () {
+ final point = Point(coordinates: Position(0, 0));
+ final out = circle(point, 10, properties: {'foo': 'bar'});
+
+ final isEqual = out.properties?['foo'] == 'bar';
+ expect(isEqual, true);
+ });
+
+ Directory inDir = Directory('./test/examples/circle/in');
+ for (var file in inDir.listSync(recursive: true)) {
+ if (file is File && file.path.endsWith('.geojson')) {
+ test(
+ file.path,
+ () {
+ final inSource = file.readAsStringSync();
+ final feature = Feature.fromJson(jsonDecode(inSource));
+ final properties = feature.properties ?? {};
+ final radius = properties['radius'] ?? 5;
+ final steps = properties['steps'] ?? 64;
+ final unit = properties['units'];
+
+ final C = truncate(circle(feature, radius,
+ properties: {"marker-symbol": "circle"},
+ steps: steps,
+ unit: unit)) as Feature<Polygon>;
+
+ final results = featureCollection([feature, C]);
+
+ Directory outDir = Directory('./test/examples/centroid/out');
+ for (var file2 in outDir.listSync(recursive: true)) {
+ if (file2 is File &&
+ file2.uri.pathSegments.last == file.uri.pathSegments.last) {
+ var outSource = file2.readAsStringSync();
+ var outGeom = GeoJSONObject.fromJson(jsonDecode(outSource));
+ Equality eq = Equality();
+ expect(eq.compare(results, outGeom), true);
+ }
+ }
+ },
+ );
+ }
+ }
+ },
+ );
+}

test/examples/circle/in/circle1.geojson

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+{
+ "type": "Feature",
+ "properties": {
+ "radius": 5
+ },
+ "geometry": {
+ "type": "Point",
+ "coordinates": [-75.343, 39.984]
+ }
+}

test/examples/circle/out/circle1.geojson

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+{
+ "type": "FeatureCollection",
+ "features": [
+ {
+ "type": "Feature",
+ "properties": {
+ "radius": 5
+ },
+ "geometry": {
+ "type": "Point",
+ "coordinates": [-75.343, 39.984]
+ }
+ },
+ {
+ "type": "Feature",
+ "properties": {
+ "radius": 5
+ },
+ "geometry": {
+ "type": "Polygon",
+ "coordinates": [
+ [
+ [-75.343, 40.028966],
+ [-75.348756, 40.028749],
+ [-75.354456, 40.028101],
+ [-75.360046, 40.027029],
+ [-75.365472, 40.025541],
+ [-75.37068, 40.023653],
+ [-75.375622, 40.021383],
+ [-75.380248, 40.018753],
+ [-75.384516, 40.015788],
+ [-75.388383, 40.012517],
+ [-75.391813, 40.008972],
+ [-75.394772, 40.005185],
+ [-75.397232, 40.001195],
+ [-75.399169, 39.997039],
+ [-75.400565, 39.992758],
+ [-75.401406, 39.988393],
+ [-75.401685, 39.983985],
+ [-75.401399, 39.979578],
+ [-75.40055, 39.975213],
+ [-75.399148, 39.970934],
+ [-75.397204, 39.96678],
+ [-75.39474, 39.962792],
+ [-75.391777, 39.959008],
+ [-75.388345, 39.955465],
+ [-75.384477, 39.952197],
+ [-75.380211, 39.949235],
+ [-75.375586, 39.946608],
+ [-75.370648, 39.94434],
+ [-75.365444, 39.942455],
+ [-75.360025, 39.940969],
+ [-75.354442, 39.939897],
+ [-75.348748, 39.93925],
+ [-75.343, 39.939034],
+ [-75.337252, 39.93925],
+ [-75.331558, 39.939897],
+ [-75.325975, 39.940969],
+ [-75.320556, 39.942455],
+ [-75.315352, 39.94434],
+ [-75.310414, 39.946608],
+ [-75.305789, 39.949235],
+ [-75.301523, 39.952197],
+ [-75.297655, 39.955465],
+ [-75.294223, 39.959008],
+ [-75.29126, 39.962792],
+ [-75.288796, 39.96678],
+ [-75.286852, 39.970934],
+ [-75.28545, 39.975213],
+ [-75.284601, 39.979578],
+ [-75.284315, 39.983985],
+ [-75.284594, 39.988393],
+ [-75.285435, 39.992758],
+ [-75.286831, 39.997039],
+ [-75.288768, 40.001195],
+ [-75.291228, 40.005185],
+ [-75.294187, 40.008972],
+ [-75.297617, 40.012517],
+ [-75.301484, 40.015788],
+ [-75.305752, 40.018753],
+ [-75.310378, 40.021383],
+ [-75.31532, 40.023653],
+ [-75.320528, 40.025541],
+ [-75.325954, 40.027029],
+ [-75.331544, 40.028101],
+ [-75.337244, 40.028749],
+ [-75.343, 40.028966]
+ ]
+ ]
+ }
+ }
+ ]
+}