Merge pull request #26 from wingkwong/develop

0.6.0

Author: wingkwong

CHANGELOG.md

@@ -1,9 +1,14 @@
 # CHANGELOG
 
+## 0.6.0
+
+- Add findPolygonCentroid
+- Add getPolygonIntersection
+
 ## 0.5.0
-- greatCircleDistanceBetweenTwoGeoPoints
-- getRectangleBounds
-- calculateBoundingBox
+- Add greatCircleDistanceBetweenTwoGeoPoints
+- Add getRectangleBounds
+- Add calculateBoundingBox
 
 ## 0.4.2
 - Removed pedantic

README.md

@@ -148,18 +148,18 @@ Similar to PolygonEnvelop in Python
   List<LatLng> rectangleBounds = geodesy.getRectangleBounds(polygonCoords);
 ```
 
-### Great-circle distance between two points using the Haversine formula
+### greatCircleDistanceBetweenTwoGeoPoints(num lat1, num lng1, num lat2, num lng2)
 
-Calculate the Great-Circle Distance between two Geo points
+Calculate the Great-Circle Distance between two Geo points using the Haversine formula
 
 ```dart
 num latitude1 = 37.7749;
-  num longitude1 = -122.4194;
-  num latitude2 = 37.3382;
-  num longitude2 = -121.8863;
+num longitude1 = -122.4194;
+num latitude2 = 37.3382;
+num longitude2 = -121.8863;
 
-  num greatCircleDistance = geodesy.greatCircleDistanceBetweenTwoGeoPoints(
-      latitude1, longitude1, latitude2, longitude2);
+num greatCircleDistance = geodesy.greatCircleDistanceBetweenTwoGeoPoints(
+    latitude1, longitude1, latitude2, longitude2);
 ```
 
 ### calculateBoundingBox(LatLng centerPoint, num distanceInKm)
@@ -174,3 +174,43 @@ Given the Latitude and Longitude and distance in kilometers it calculate the bou
 
   final boundingBox = geodesy.calculateBoundingBox(centerPoint, distanceInKm);
 ```
+
+## findPolygonCentroid(List<LatLng> polygon)
+
+```dart
+  List<LatLng> polygon = [
+    const LatLng(0, 0),
+    const LatLng(4, 0),
+    const LatLng(4, 4),
+    const LatLng(0, 4)
+  ];
+
+  LatLng centroid = geodesy.findPolygonCentroid(polygon);
+  print("Centroid: ${centroid.latitude}, ${centroid.longitude}");
+```
+
+## getPolygonIntersection(List<LatLng> polygon1, List<LatLng> polygon2)
+
+```dart
+final List<LatLng> polygon1 = [
+    const LatLng(0, 0),
+    const LatLng(0, 2),
+    const LatLng(2, 2),
+    const LatLng(2, 0),
+  ];
+
+  final List<LatLng> polygon2 = [
+    const LatLng(1, 1),
+    const LatLng(1, 3),
+    const LatLng(3, 3),
+    const LatLng(3, 1),
+  ];
+
+  final List<LatLng> intersectionPoints =
+      geodesy.getPolygonIntersection(polygon1, polygon2);
+
+  print('Intersection Points:');
+  for (final point in intersectionPoints) {
+    print('Latitude: ${point.latitude}, Longitude: ${point.longitude}');
+  }
+```

analysis_options.yaml

@@ -2,9 +2,6 @@
 include: package:lints/core.yaml
 
 analyzer:
-  strong-mode:
-    implicit-casts: false
-    implicit-dynamic: false
   errors:
     missing_return: error
     missing_required_param: error

example/main.dart

@@ -96,4 +96,40 @@ void main() async {
   print('[calculateBoundingBox]: ');
   print(' > Top Left: ${boundingBox[0]}');
   print(' > Bottom Right: ${boundingBox[1]}');
+
+  // Polygon Centroid
+  List<LatLng> polygon = [
+    const LatLng(0, 0),
+    const LatLng(4, 0),
+    const LatLng(4, 4),
+    const LatLng(0, 4)
+  ];
+
+  LatLng centroid = geodesy.findPolygonCentroid(polygon);
+
+  print("Centroid: ${centroid.latitude}, ${centroid.longitude}");
+
+  // Polygon Intersection
+
+  final List<LatLng> polygon1 = [
+    const LatLng(0, 0),
+    const LatLng(0, 2),
+    const LatLng(2, 2),
+    const LatLng(2, 0),
+  ];
+
+  final List<LatLng> polygon2 = [
+    const LatLng(1, 1),
+    const LatLng(1, 3),
+    const LatLng(3, 3),
+    const LatLng(3, 1),
+  ];
+
+  final List<LatLng> intersectionPoints =
+      geodesy.getPolygonIntersection(polygon1, polygon2);
+
+  print('Intersection Points:');
+  for (final point in intersectionPoints) {
+    print('Latitude: ${point.latitude}, Longitude: ${point.longitude}');
+  }
 }

lib/src/geodesy.dart

@@ -250,7 +250,6 @@ class Geodesy {
   }
 
   /// GetRectangleBounds
-
   List<LatLng> getRectangleBounds(List<LatLng> polygonCoords) {
     num minLatitude = double.infinity.toDouble();
     num maxLatitude = double.negativeInfinity.toDouble();
@@ -300,4 +299,113 @@ class Geodesy {
         LatLng(bottomLat.toDouble(), rightLng.toDouble());
     return [topLeft, bottomRight];
   }
+
+  /// finds the centroid of polygons
+  LatLng findPolygonCentroid(List<LatLng> polygons) {
+    num x = 0;
+    num y = 0;
+    num signedArea = 0;
+
+    num vertexCount = polygons.length;
+
+    for (int i = 0; i < vertexCount; i++) {
+      final LatLng currentVertex = polygons[i];
+      final LatLng nextVertex = polygons[(i + 1) % vertexCount.toInt()];
+
+      num a = currentVertex.longitude * nextVertex.latitude -
+          nextVertex.longitude * currentVertex.latitude;
+      signedArea += a;
+      x += (currentVertex.longitude + nextVertex.longitude) * a;
+      y += (currentVertex.latitude + nextVertex.latitude) * a;
+    }
+
+    signedArea *= 0.5;
+    x /= (6 * signedArea);
+    y /= (6 * signedArea);
+
+    // Return the centroid as LatLng object
+    return LatLng(
+      y.toDouble(),
+      x.toDouble(),
+    );
+  }
+
+  /// Polygon Intersection
+  List<LatLng> getPolygonIntersection(
+      List<LatLng> polygon1, List<LatLng> polygon2) {
+    final List<LatLng> intersectionPoints = <LatLng>[];
+
+    for (int i = 0; i < polygon1.length; i++) {
+      final int j = (i + 1) % polygon1.length;
+      final LatLng edge1Start = polygon1[i];
+      final LatLng edge1End = polygon1[j];
+
+      for (int k = 0; k < polygon2.length; k++) {
+        final int l = (k + 1) % polygon2.length;
+        final LatLng edge2Start = polygon2[k];
+        final LatLng edge2End = polygon2[l];
+
+        final LatLng? intersection =
+            _getLineIntersection(edge1Start, edge1End, edge2Start, edge2End);
+        if (intersection != null) {
+          intersectionPoints.add(intersection);
+        }
+      }
+    }
+    return intersectionPoints;
+  }
+
+  LatLng? _getLineIntersection(
+      LatLng start1, LatLng end1, LatLng start2, LatLng end2) {
+    final num x1 = start1.latitude;
+    final num y1 = start1.longitude;
+    final num x2 = end1.latitude;
+    final num y2 = end1.longitude;
+    final num x3 = start2.latitude;
+    final num y3 = start2.longitude;
+    final num x4 = end2.latitude;
+    final num y4 = end2.longitude;
+
+    final num denominator = (x1 - x2) * (y3 - y4) - (y1 - y2) * (x3 - x4);
+    if (denominator == 0) {
+      return null; // Lines are parallel or coincident
+    }
+
+    final num intersectionX =
+        ((x1 * y2 - y1 * x2) * (x3 - x4) - (x1 - x2) * (x3 * y4 - y3 * x4)) /
+            denominator;
+    final num intersectionY =
+        ((x1 * y2 - y1 * x2) * (y3 - y4) - (y1 - y2) * (x3 * y4 - y3 * x4)) /
+            denominator;
+
+    final LatLng intersection =
+        LatLng(intersectionX.toDouble(), intersectionY.toDouble());
+
+    if (_isPointOnLine(intersection, start1, end1) &&
+        _isPointOnLine(intersection, start2, end2)) {
+      return intersection;
+    } else {
+      return null;
+    }
+  }
+
+  bool _isPointOnLine(LatLng point, LatLng lineStart, LatLng lineEnd) {
+    final minX = lineStart.latitude < lineEnd.latitude
+        ? lineStart.latitude
+        : lineEnd.latitude;
+    final maxX = lineStart.latitude > lineEnd.latitude
+        ? lineStart.latitude
+        : lineEnd.latitude;
+    final minY = lineStart.longitude < lineEnd.longitude
+        ? lineStart.longitude
+        : lineEnd.longitude;
+    final maxY = lineStart.longitude > lineEnd.longitude
+        ? lineStart.longitude
+        : lineEnd.longitude;
+
+    return point.latitude >= minX &&
+        point.latitude <= maxX &&
+        point.longitude >= minY &&
+        point.longitude <= maxY;
+  }
 }

pubspec.yaml

@@ -1,6 +1,6 @@
 name: geodesy
 description: A Dart library for geodesic and trigonometric calculations working with points and paths
-version: 0.5.0
+version: 0.6.0
 homepage: https://github.com/wingkwong/geodesy
 
 environment:

test/geodesy_test.dart

@@ -164,4 +164,48 @@ void main() {
     });
   });
 
+// Polygon Centroid
+
+  test('findPolygonCentroid calculates the centroid correctly', () {
+    // Create a test polygon
+    List<LatLng> polygon = [
+      const LatLng(0, 0),
+      const LatLng(0, 4),
+      const LatLng(4, 4),
+      const LatLng(4, 0),
+    ];
+
+    // Calculate the centroid
+    LatLng centroid = geodesy.findPolygonCentroid(polygon);
+
+    // Verify the centroid coordinates
+    expect(centroid.latitude, equals(2.0));
+    expect(centroid.longitude, equals(2.0));
+  });
+
+  // Polygon Intersection
+  test('Intersection of two polygons', () {
+    final polygon1 = [
+      const LatLng(0, 0),
+      const LatLng(0, 2),
+      const LatLng(2, 2),
+      const LatLng(2, 0),
+    ];
+
+    final polygon2 = [
+      const LatLng(1, 1),
+      const LatLng(1, 3),
+      const LatLng(3, 3),
+      const LatLng(3, 1),
+    ];
+
+    final intersectionPoints =
+        geodesy.getPolygonIntersection(polygon1, polygon2);
+
+    expect(intersectionPoints.length, 2);
+    expect(intersectionPoints[0].latitude, 1);
+    expect(intersectionPoints[0].longitude, 2);
+    expect(intersectionPoints[1].latitude, 2);
+    expect(intersectionPoints[1].longitude, 1);
+  });
 }