Added MapController.pointToLatLng() to get LatLng of given screen point

example/lib/main.dart

@@ -2,6 +2,7 @@ import 'package:flutter/material.dart';
 import 'package:flutter_map_example/pages/epsg4326_crs.dart';
 import 'package:flutter_map_example/pages/map_inside_listview.dart';
 import 'package:flutter_map_example/pages/network_tile_provider.dart';
+import 'package:flutter_map_example/pages/point_to_latlng.dart';
 
 import './pages/animated_map_controller.dart';
 import './pages/circle.dart';
@@ -82,6 +83,7 @@ class MyApp extends StatelessWidget {
         ResetTileLayerPage.route: (context) => const ResetTileLayerPage(),
         EPSG4326Page.route: (context) => const EPSG4326Page(),
         MaxBoundsPage.route: (context) => const MaxBoundsPage(),
+        PointToLatLngPage.route: (context) => const PointToLatLngPage(),
       },
     );
   }

example/lib/pages/point_to_latlng.dart

@@ -0,0 +1,134 @@
+import 'dart:async';
+
+import 'package:flutter/material.dart';
+import 'package:flutter_map/flutter_map.dart';
+import 'package:latlong2/latlong.dart';
+
+import '../widgets/drawer.dart';
+
+class PointToLatLngPage extends StatefulWidget {
+  static const String route = 'point_to_latlng';
+
+  const PointToLatLngPage({Key? key}) : super(key: key);
+
+  @override
+  PointToLatlngPage createState() {
+    return PointToLatlngPage();
+  }
+}
+
+class PointToLatlngPage extends State<PointToLatLngPage> {
+  late final MapController mapController;
+  late final StreamSubscription mapEventSubscription;
+  final pointSize = 40.0;
+  final pointY = 200.0;
+
+  LatLng? latLng;
+
+  @override
+  void initState() {
+    super.initState();
+    mapController = MapController();
+
+    mapEventSubscription = mapController.mapEventStream
+        .listen((mapEvent) => onMapEvent(mapEvent, context));
+
+    Future.delayed(Duration.zero, () {
+      mapController.onReady.then((_) => _updatePointLatLng(context));
+    });
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+      appBar: AppBar(title: const Text('PointToLatlng')),
+      floatingActionButton: Column(
+        mainAxisAlignment: MainAxisAlignment.end,
+        children: [
+          FloatingActionButton(
+            child: const Icon(Icons.rotate_right),
+            onPressed: () => mapController.rotate(60.0),
+          ),
+          const SizedBox(height: 15),
+          FloatingActionButton(
+            child: const Icon(Icons.cancel),
+            onPressed: () => mapController.rotate(0.0),
+          ),
+        ],
+      ),
+      drawer: buildDrawer(context, PointToLatLngPage.route),
+      body: Stack(
+        children: [
+          FlutterMap(
+            mapController: mapController,
+            options: MapOptions(
+              center: LatLng(51.5, -0.09),
+              zoom: 5.0,
+              minZoom: 3.0,
+            ),
+            children: [
+              TileLayerWidget(
+                  options: TileLayerOptions(
+                      urlTemplate:
+                          'https://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png',
+                      subdomains: ['a', 'b', 'c'])),
+              if (latLng != null)
+                MarkerLayerWidget(
+                    options: MarkerLayerOptions(
+                  markers: [
+                    Marker(
+                      width: pointSize,
+                      height: pointSize,
+                      point: latLng!,
+                      builder: (ctx) => const FlutterLogo(),
+                    )
+                  ],
+                ))
+            ],
+          ),
+          Container(
+              color: Colors.white,
+              height: 60,
+              child: Center(
+                  child: Column(
+                mainAxisAlignment: MainAxisAlignment.center,
+                children: [
+                  Text(
+                    'flutter logo (${latLng?.latitude.toStringAsPrecision(4)},${latLng?.longitude.toStringAsPrecision(4)})',
+                    textAlign: TextAlign.center,
+                  ),
+                ],
+              ))),
+          Positioned(
+              top: pointY - pointSize / 2,
+              left: _getPointX(context) - pointSize / 2,
+              child: Icon(Icons.crop_free, size: pointSize))
+        ],
+      ),
+    );
+  }
+
+  void onMapEvent(MapEvent mapEvent, BuildContext context) {
+    _updatePointLatLng(context);
+  }
+
+  void _updatePointLatLng(context) {
+    final pointX = _getPointX(context);
+
+    final latLng = mapController.pointToLatLng(CustomPoint(pointX, pointY));
+
+    setState(() {
+      this.latLng = latLng;
+    });
+  }
+
+  double _getPointX(BuildContext context) {
+    return MediaQuery.of(context).size.width / 2;
+  }
+
+  @override
+  void dispose() {
+    super.dispose();
+    mapEventSubscription.cancel();
+  }
+}

example/lib/widgets/drawer.dart

@@ -3,6 +3,7 @@ import 'package:flutter_map_example/pages/epsg4326_crs.dart';
 import 'package:flutter_map_example/pages/map_inside_listview.dart';
 import 'package:flutter_map_example/pages/marker_rotate.dart';
 import 'package:flutter_map_example/pages/network_tile_provider.dart';
+import 'package:flutter_map_example/pages/point_to_latlng.dart';
 
 import '../pages/animated_map_controller.dart';
 import '../pages/circle.dart';
@@ -250,6 +251,8 @@ Drawer buildDrawer(BuildContext context, String currentRoute) {
         ),
         _buildMenuItem(context, const Text('Map inside listview'),
             MapInsideListViewPage.route, currentRoute),
+        _buildMenuItem(context, const Text('Point to LatLng'),
+            PointToLatLngPage.route, currentRoute),
       ],
     ),
   );

lib/flutter_map.dart

@@ -5,6 +5,7 @@ import 'dart:math';
 
 import 'package:flutter/widgets.dart';
 import 'package:flutter_map/src/core/center_zoom.dart';
+import 'package:flutter_map/src/core/point.dart';
 import 'package:flutter_map/src/geo/crs/crs.dart';
 import 'package:flutter_map/src/geo/latlng_bounds.dart';
 import 'package:flutter_map/src/gestures/interactive_flag.dart';
@@ -148,6 +149,8 @@ abstract class MapController {
   set state(MapState state);
   void dispose();
 
+  LatLng? pointToLatLng(CustomPoint point);
+
   factory MapController() => MapControllerImpl();
 }
 

lib/src/map/map.dart

@@ -78,6 +78,42 @@ class MapControllerImpl implements MapController {
     return _state.rotate(degree, id: id, source: MapEventSource.mapController);
   }
 
+  @override
+  LatLng? pointToLatLng(CustomPoint localPoint) {
+    if (_state.originalSize == null) {
+      return null;
+    }
+
+    final width = _state.originalSize!.x;
+    final height = _state.originalSize!.y;
+
+    final localPointCenterDistance =
+        CustomPoint((width / 2) - localPoint.x, (height / 2) - localPoint.y);
+    final mapCenter =
+        _state.options.crs.latLngToPoint(_state.center, _state.zoom);
+
+    var point = mapCenter - localPointCenterDistance;
+
+    if (_state.rotation != 0.0) {
+      point = rotatePoint(mapCenter, point);
+    }
+
+    return _state.options.crs.pointToLatLng(point, _state.zoom);
+  }
+
+  CustomPoint<num> rotatePoint(
+      CustomPoint<num> mapCenter, CustomPoint<num> point) {
+    final m = Matrix4.identity()
+      ..translate(mapCenter.x.toDouble(), mapCenter.y.toDouble())
+      ..rotateZ(-_state.rotationRad)
+      ..translate(-mapCenter.x.toDouble(), -mapCenter.y.toDouble());
+
+    final tp = MatrixUtils.transformPoint(
+        m, Offset(point.x.toDouble(), point.y.toDouble()));
+
+    return CustomPoint(tp.dx, tp.dy);
+  }
+
   @override
   Stream<MapEvent> get mapEventStream => _mapEventSink.stream;
 }