feat(geobase): project bounding box #96

dart/geobase/CHANGELOG.md

@@ -21,6 +21,7 @@ NOTE: Version 0.5.0 currently [under development](https://github.com/navibyte/ge
 * [Alternative logics to resolve axis order #182](https://github.com/navibyte/geospatial/issues/182)
 * [Handle explicit and implicit bounds in geometries and features on geobase #141](https://github.com/navibyte/geospatial/issues/141)
 * [Add project method for Position class #184](https://github.com/navibyte/geospatial/issues/184)
+* [Project bounding box #96](https://github.com/navibyte/geospatial/issues/96)
 
 🛠 Refactoring:
 * [Enforce "geometry" under "Feature" when encoding GeoJSON text output #91](https://github.com/navibyte/geospatial/issues/91)

dart/geobase/lib/src/coordinates/base/box.dart

@@ -10,6 +10,7 @@ import 'dart:math' as math;
 
 import '/src/codes/coords.dart';
 import '/src/constants/epsilon.dart';
+import '/src/coordinates/projection/projection.dart';
 import '/src/utils/format_validation.dart';
 import '/src/utils/num.dart';
 import '/src/utils/tolerance.dart';
@@ -161,6 +162,13 @@ abstract class Box extends Positionable {
   /// equals between min and max) or 4 positions (otherwise).
   Iterable<Position> get corners2D;
 
+  /// Projects this bounding box to another box using [projection].
+  ///
+  /// Subtypes may specify a more accurate bounding box type for the returned
+  /// object (for example a *geographic* bounding box would return a *projected*
+  /// box when forward-projecting, and other way when inverse-projecting).
+  Box project(Projection projection);
+
   /// True if this box equals with [other] by testing 2D coordinates only.
   ///
   /// Differences on 2D coordinate values (ie. x and y, or lon and lat) between

dart/geobase/lib/src/coordinates/base/position.dart

@@ -176,7 +176,7 @@ abstract class Position extends Positionable {
   /// measured position.
   Position copyWith({num? x, num? y, num? z, num? m});
 
-  /// Projects this position to another position using the [projection].
+  /// Projects this position to another position using [projection].
   ///
   /// Subtypes may specify a more accurate position type for the returned object
   /// (for example a *geographic* position would return a *projected* position

dart/geobase/lib/src/coordinates/geographic/geobox.dart

@@ -9,6 +9,8 @@ import 'package:meta/meta.dart';
 import '/src/codes/coords.dart';
 import '/src/coordinates/base/aligned.dart';
 import '/src/coordinates/base/box.dart';
+import '/src/coordinates/projected/projbox.dart';
+import '/src/coordinates/projection/projection.dart';
 
 import 'dms.dart';
 import 'geographic.dart';
@@ -255,6 +257,21 @@ class GeoBox extends Box {
   Iterable<Geographic> get corners2D =>
       Box.createCorners2D(this, Geographic.create);
 
+  /// Projects this geographic bounding box to a projected box using
+  /// the forward [projection].
+  @override
+  ProjBox project(Projection projection) {
+    // get distinct corners (one, two or four) in 2D for the geographic bbox
+    final corners = corners2D;
+
+    // project all corner positions (using the forward projection)
+    final projected = corners.map((pos) => pos.project(projection));
+
+    // create a projected bbox
+    // (calculating min and max coords in all axes from corner positions)
+    return ProjBox.from(projected);
+  }
+
   @override
   int get spatialDimension => type.spatialDimension;
 

dart/geobase/lib/src/coordinates/projected/projbox.dart

@@ -9,6 +9,8 @@ import 'package:meta/meta.dart';
 import '/src/codes/coords.dart';
 import '/src/coordinates/base/aligned.dart';
 import '/src/coordinates/base/box.dart';
+import '/src/coordinates/geographic/geobox.dart';
+import '/src/coordinates/projection/projection.dart';
 
 import 'projected.dart';
 
@@ -195,6 +197,21 @@ class ProjBox extends Box {
   Iterable<Projected> get corners2D =>
       Box.createCorners2D(this, Projected.create);
 
+  /// Projects this projected bounding box to a geographic box using
+  /// the inverse [projection].
+  @override
+  GeoBox project(Projection projection) {
+    // get distinct corners (one, two or four) in 2D for the projected bbox
+    final corners = corners2D;
+
+    // unproject all corner positions (using the inverse projection)
+    final unprojected = corners.map((pos) => pos.project(projection));
+
+    // create an unprojected (geographic) bbox
+    // (calculating min and max coords in all axes from corner positions)
+    return GeoBox.from(unprojected);
+  }
+
   @override
   int get spatialDimension => type.spatialDimension;
 

dart/geobase/lib/src/vector_data/array/box_coords.dart

@@ -94,6 +94,12 @@ abstract class BoxCoords extends Box with _CoordinatesMixin {
     return BoxCoords.view(list, type: type);
   }
 
+  /// A minimum bounding box calculated from [positions].
+  ///
+  /// Throws FormatException if cannot create (ie. [positions] is empty).
+  factory BoxCoords.from(Iterable<Position> positions) =>
+      Box.createBoxFrom(positions, BoxCoords.create);
+
   /// Parses a bounding box with coordinate values parsed from [text].
   ///
   /// Coordinate values in [text] are separated by [delimiter].
@@ -177,6 +183,20 @@ class _BoxCoordsImpl extends BoxCoords {
   Iterable<Position> get corners2D =>
       Box.createCorners2D(this, Projected.create);
 
+  /// Projects this bounding box to another box using [projection].
+  @override
+  BoxCoords project(Projection projection) {
+    // get distinct corners (one, two or four) in 2D for the bounding bbox
+    final corners = corners2D;
+
+    // project all corner positions (using the projection)
+    final projected = corners.map((pos) => pos.project(projection));
+
+    // create a new bounding bbox
+    // (calculating min and max coords in all axes from corner positions)
+    return BoxCoords.from(projected);
+  }
+
   @override
   PositionCoords get min => _doCreateRange(
         _data,

dart/geobase/test/projections/projection_web_mercator_test.dart

@@ -13,8 +13,10 @@ import 'projection_sample.dart';
 
 void main() {
   group('Test projections between WGS84 and Web Mercator', () {
+    final toWebMercator = WGS84.webMercator.forward;
+    final toWgs84 = WGS84.webMercator.inverse;
+
     test('webMercatorToWgs84(Projected to Geographic)', () {
-      final toWgs84 = WGS84.webMercator.inverse;
       for (final coords in wgs84ToWebMercatorData) {
         final point2 = Projected(x: coords[2], y: coords[3]);
         final geoPoint2 = Geographic(lon: coords[0], lat: coords[1]);
@@ -37,7 +39,6 @@ void main() {
     });
 
     test('wgs84ToWebMercator(Geographic to Projected)', () {
-      final toWebMercator = WGS84.webMercator.forward;
       for (final coords in wgs84ToWebMercatorData) {
         final geoPoint3 = Geographic(lon: coords[0], lat: coords[1]);
         final point3 = Projected(x: coords[2], y: coords[3]);
@@ -53,6 +54,19 @@ void main() {
         );
       }
     });
+
+    test('project bbox between GeoBox and ProjBox', () {
+      const gb = GeoBox(
+        west: 10.19238847,
+        south: -11.349348834,
+        east: 15.23095884,
+        north: 21.094852974,
+      );
+      final wm = gb.project(toWebMercator);
+      final gb2 = wm.project(toWgs84);
+      expect(gb.toText(decimals: 8), gb2.toText(decimals: 8));
+      expect(gb.equals2D(gb2), true);
+    });
   });
 
   group('Test flat coordinate arrays', () {