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Implement Square (#213)
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‎lib/square.dart‎

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library turf_square;
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export 'package:geotypes/geotypes.dart';
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export 'src/square.dart';

‎lib/src/square.dart‎

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import 'package:turf/distance.dart';
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import 'package:turf/turf.dart';
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/// Takes a [BBox] and returns a square [BBox] of equal dimensions.
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BBox square(BBox bbox) {
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final horizontalDistance = distance(
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Point(coordinates: Position.named(lng: bbox.lng1, lat: bbox.lat1)),
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Point(coordinates: Position.named(lng: bbox.lng2, lat: bbox.lat1))
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);
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final verticalDistance = distance(
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Point(coordinates: Position.named(lng: bbox.lng1, lat: bbox.lat1)),
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Point(coordinates: Position.named(lng: bbox.lng1, lat: bbox.lat2))
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);
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if (horizontalDistance >= verticalDistance) {
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final verticalMidpoint = (bbox.lat1 + bbox.lat2) / 2;
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return BBox.named(
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lng1: bbox.lng1,
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lat1: verticalMidpoint - (bbox.lng2 - bbox.lng1) / 2,
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lng2: bbox.lng2,
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lat2: verticalMidpoint + (bbox.lng2 - bbox.lng1) / 2,
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);
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} else {
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final horizontalMidpoint = (bbox.lng1 + bbox.lng2) / 2;
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return BBox.named(
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lng1: horizontalMidpoint - (bbox.lat2 - bbox.lat1) / 2,
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lat1: bbox.lat1,
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lng2: horizontalMidpoint + (bbox.lat2 - bbox.lat1) / 2,
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lat2: bbox.lat2,
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);
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}
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}

‎lib/turf.dart‎

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@@ -32,5 +32,6 @@ export 'point_to_line_distance.dart';
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export 'polygon_smooth.dart';
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export 'polygon_to_line.dart';
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export 'polyline.dart';
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export 'square.dart';
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export 'transform.dart';
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export 'truncate.dart';

‎test/components/square_test.dart‎

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import 'dart:convert';
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import 'dart:io';
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import 'package:test/test.dart';
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import 'package:turf/turf.dart';
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void main() {
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group('Square BBox Transformation', () {
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// Unit tests for specific scenarios
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test('Square a horizontal rectangle', () {
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// Input: Rectangle wider than tall
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final bbox = BBox.named(lng1: 0, lat1: 0, lng2: 10, lat2: 5);
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final squaredBBox = square(bbox);
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// Verify square dimensions
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expect(squaredBBox.lng2 - squaredBBox.lng1,
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squaredBBox.lat2 - squaredBBox.lat1,
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reason: 'BBox should be a perfect square');
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// Verify center point remains the same
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expect((squaredBBox.lng1 + squaredBBox.lng2) / 2,
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(bbox.lng1 + bbox.lng2) / 2,
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reason: 'Center longitude should remain the same');
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expect((squaredBBox.lat1 + squaredBBox.lat2) / 2,
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(bbox.lat1 + bbox.lat2) / 2,
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reason: 'Center latitude should remain the same');
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});
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test('Square a vertical rectangle', () {
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// Input: Rectangle taller than wide
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final bbox = BBox.named(lng1: 0, lat1: 0, lng2: 5, lat2: 10);
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final squaredBBox = square(bbox);
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// Verify square dimensions
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expect(squaredBBox.lng2 - squaredBBox.lng1,
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squaredBBox.lat2 - squaredBBox.lat1,
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reason: 'BBox should be a perfect square');
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// Verify center point remains the same
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expect((squaredBBox.lng1 + squaredBBox.lng2) / 2,
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(bbox.lng1 + bbox.lng2) / 2,
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reason: 'Center longitude should remain the same');
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expect((squaredBBox.lat1 + squaredBBox.lat2) / 2,
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(bbox.lat1 + bbox.lat2) / 2,
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reason: 'Center latitude should remain the same');
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});
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test('Square an already square BBox', () {
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// Input: Already square BBox
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final bbox = BBox.named(lng1: 0, lat1: 0, lng2: 10, lat2: 10);
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final squaredBBox = square(bbox);
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// Verify dimensions remain the same
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expect(squaredBBox.lng2 - squaredBBox.lng1,
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squaredBBox.lat2 - squaredBBox.lat1,
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reason: 'BBox should remain a square');
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expect(squaredBBox.lng1, bbox.lng1);
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expect(squaredBBox.lat1, bbox.lat1);
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expect(squaredBBox.lng2, bbox.lng2);
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expect(squaredBBox.lat2, bbox.lat2);
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});
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test('Square a BBox with negative coordinates', () {
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// Input: BBox with negative coordinates
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final bbox = BBox.named(lng1: -10, lat1: -5, lng2: 0, lat2: 5);
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final squaredBBox = square(bbox);
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// Verify square dimensions
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expect(squaredBBox.lng2 - squaredBBox.lng1,
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squaredBBox.lat2 - squaredBBox.lat1,
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reason: 'BBox should be a perfect square');
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// Verify center point remains the same
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expect((squaredBBox.lng1 + squaredBBox.lng2) / 2,
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(bbox.lng1 + bbox.lng2) / 2,
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reason: 'Center longitude should remain the same');
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expect((squaredBBox.lat1 + squaredBBox.lat2) / 2,
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(bbox.lat1 + bbox.lat2) / 2,
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reason: 'Center latitude should remain the same');
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});
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// File-based test for real-world scenarios
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// File-based test for real-world scenarios
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group('File-based Tests', () {
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var inDir = Directory('./test/examples/square/in');
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if (inDir.existsSync()) {
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for (var file in inDir.listSync(recursive: true)) {
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if (file is File && file.path.endsWith('.geojson')) {
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test(file.path, () {
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var inSource = file.readAsStringSync();
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var inJson = jsonDecode(inSource);
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// Get the first feature
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var feature = inJson['features'][0];
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if (feature['geometry']['bbox'] == null) {
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throw Exception("Missing 'bbox' in GeoJSON feature geometry");
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}
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// Extract bbox from the geometry
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var bbox = feature['geometry']['bbox'];
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// Create BBox instance
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var geoBbox = BBox.named(
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lng1: bbox[0], // min longitude
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lat1: bbox[1], // min latitude
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lng2: bbox[2], // max longitude
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lat2: bbox[3], // max latitude
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);
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// Perform square operation (this doesn't change geometry type)
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BBox squaredBBox = square(geoBbox);
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// Create updated feature with new bbox but original geometry
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var updatedFeature = Map<String, dynamic>.from(feature);
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updatedFeature['geometry'] =
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Map<String, dynamic>.from(feature['geometry']);
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updatedFeature['geometry']['bbox'] = [
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squaredBBox.lng1,
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squaredBBox.lat1,
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squaredBBox.lng2,
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squaredBBox.lat2,
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];
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// Prepare output path
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var outPath = file.path.replaceAll('/in', '/out');
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var outFile = File(outPath);
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if (!outFile.existsSync()) {
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print('Warning: Output file not found at $outPath');
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return;
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}
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var outSource = outFile.readAsStringSync();
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var expectedOutput = jsonDecode(outSource);
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var expectedFeature = expectedOutput['features'][0];
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// Verify feature collection structure
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expect(expectedOutput['type'], 'FeatureCollection');
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// Compare geometry types (should remain unchanged)
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expect(
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updatedFeature['geometry']['type'],
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expectedFeature['geometry']['type'],
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reason: 'Geometry type should remain the same',
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);
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// Compare coordinates (should remain unchanged)
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expect(
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updatedFeature['geometry']['coordinates'],
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expectedFeature['geometry']['coordinates'],
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reason: 'Coordinates should remain unchanged',
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);
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// Compare the updated bbox values
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expect(
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updatedFeature['geometry']['bbox'],
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expectedFeature['geometry']['bbox'],
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reason: 'BBox should match expected squared version',
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);
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});
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}
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}
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}
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});
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});
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}

‎test/examples/square/in/horizontalrectangle.geojson‎

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{
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"type": "FeatureCollection",
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"features": [
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{
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"type": "Feature",
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"properties": {},
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"geometry": {
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"type": "LineString",
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"coordinates": [
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[
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100.0,
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0
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],
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[
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110.0,
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1
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]
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],
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"bbox": [
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100.0,
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0.0,
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110.0,
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1.0
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]
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}
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}
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]
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}
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‎test/examples/square/in/verticalrectangle.geojson‎

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{
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"type": "FeatureCollection",
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"features": [
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{
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"type": "Feature",
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"properties": {},
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"geometry": {
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"type": "LineString",
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"coordinates": [
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[
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100,
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0
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],
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[
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101,
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10
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]
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],
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"bbox": [
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95.5,
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0,
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105.5,
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10
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]
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}
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}
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]
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}

‎test/examples/square/out/horizontalrectangle.geojson‎

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{
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"type": "FeatureCollection",
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"features": [
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{
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"type": "Feature",
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"properties": {},
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"geometry": {
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"type": "LineString",
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"coordinates": [
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[
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100,
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0
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],
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[
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110,
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1
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]
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],
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"bbox": [
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100.0,
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-4.5,
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110.0,
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5.5
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]
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}
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}
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]
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}
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‎test/examples/square/out/verticalrectangle.geojson‎

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{
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"type": "FeatureCollection",
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"features": [
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{
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"type": "Feature",
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"properties": {},
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"geometry": {
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"type": "LineString",
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"coordinates": [
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[
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100,
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0
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],
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[
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101,
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10
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]
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],
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"bbox": [
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95.5,
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0,
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105.5,
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10
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]
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}
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}
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]
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}

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