Init

lib/main.dart

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+import 'dart:async';
+import 'dart:io';
+import 'dart:isolate';
+
+import 'package:file_picker/file_picker.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_ffmpeg/stream_information.dart';
+import 'package:flutter_opencv_example/native_opencv.dart';
+import 'package:path_provider/path_provider.dart';
+import 'package:flutter_ffmpeg/flutter_ffmpeg.dart';
+
+const title = 'Native OpenCV Example';
+
+late Directory tempDir;
+
+String get dataPath => '${tempDir.path}/data.csv';
+
+void main() {
+  WidgetsFlutterBinding.ensureInitialized();
+  getTemporaryDirectory().then((dir) => tempDir = dir);
+
+  runApp(MyApp());
+}
+
+class MyApp extends StatelessWidget {
+  @override
+  Widget build(BuildContext context) {
+    return MaterialApp(
+      title: title,
+      theme: ThemeData(
+        primarySwatch: Colors.blue,
+      ),
+      home: MyHomePage(),
+    );
+  }
+}
+
+class MyHomePage extends StatefulWidget {
+  @override
+  _MyHomePageState createState() => _MyHomePageState();
+}
+
+class _MyHomePageState extends State<MyHomePage> {
+  bool _isProcessed = false;
+  bool _isWorking = false;
+
+  void showVersion() {
+    final scaffoldMessenger = ScaffoldMessenger.of(context);
+    final snackbar = SnackBar(
+      content: Text('OpenCV version: ${opencvVersion()}'),
+    );
+
+    scaffoldMessenger
+      ..removeCurrentSnackBar(reason: SnackBarClosedReason.dismiss)
+      ..showSnackBar(snackbar);
+  }
+
+  Future<String?> pickAnImage() async {
+    if (Platform.isIOS || Platform.isAndroid) {
+      return FilePicker.platform
+          .pickFiles(
+            dialogTitle: 'Pick an image',
+            type: FileType.video,
+            allowMultiple: false,
+          )
+          .then((v) => v?.files.first.path);
+    } else {
+      return FilePicker.platform
+          .pickFiles(
+            dialogTitle: 'Pick an image',
+            type: FileType.image,
+            allowMultiple: false,
+          )
+          .then((v) => v?.files.first.path);
+    }
+  }
+
+  Future<void> takeImageAndProcess() async {
+    final imagePath = await pickAnImage();
+    final FlutterFFprobe _flutterFFmpeg = FlutterFFprobe();
+
+    if (imagePath == null) {
+      return;
+    }
+
+    double? frameRate;
+    var vinfo = await _flutterFFmpeg.getMediaInformation(imagePath);
+    List<StreamInformation>? streams = vinfo.getStreams();
+    if (streams!.length > 0) {
+      for (var stream in streams) {
+        if (stream.getAllProperties()['codec_type'] == "video") {
+          frameRate = int.parse(
+                  stream.getAllProperties()['avg_frame_rate'].split("/")[0]) /
+              int.parse(
+                  stream.getAllProperties()['avg_frame_rate'].split("/")[1]);
+        }
+      }
+    }
+    setState(() {
+      _isWorking = true;
+    });
+
+    // Creating a port for communication with isolate and arguments for entry point
+    final port = ReceivePort();
+    final args = ProcessImageArguments(imagePath, dataPath, frameRate ?? 0.0);
+
+    // Spawning an isolate
+    Isolate.spawn<ProcessImageArguments>(
+      processImage,
+      args,
+      onError: port.sendPort,
+      onExit: port.sendPort,
+    );
+
+    // Making a variable to store a subscription in
+    late StreamSubscription sub;
+
+    // Listening for messages on port
+    sub = port.listen((_) async {
+      // Cancel a subscription after message received called
+      await sub.cancel();
+
+      setState(() {
+        _isProcessed = true;
+        _isWorking = false;
+      });
+    });
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+      appBar: AppBar(title: Text(title)),
+      body: Stack(
+        children: <Widget>[
+          Center(
+            child: ListView(
+              shrinkWrap: true,
+              children: <Widget>[
+                if (_isProcessed && !_isWorking)
+                  ConstrainedBox(
+                    constraints: BoxConstraints(maxWidth: 3000, maxHeight: 300),
+                    // child: Image.file(
+                    //   File(tempPath),
+                    //   alignment: Alignment.center,
+                    // ),
+                  ),
+                Column(
+                  children: [
+                    ElevatedButton(
+                      child: Text('Show version'),
+                      onPressed: showVersion,
+                    ),
+                    ElevatedButton(
+                      child: Text('Process photo'),
+                      onPressed: takeImageAndProcess,
+                    ),
+                  ],
+                )
+              ],
+            ),
+          ),
+          if (_isWorking)
+            Positioned.fill(
+              child: Container(
+                color: Colors.black.withOpacity(.7),
+                child: Center(
+                  child: CircularProgressIndicator(),
+                ),
+              ),
+            ),
+        ],
+      ),
+    );
+  }
+}