opencv_dart 1.2.2

OpenCV4 bindings for Dart language and Flutter, using dart:ffi. The most complete OpenCV bindings for Dart! With asynchronous support now!

example/lib/main.dart

// ignore_for_file: avoid_print

import 'dart:isolate';
import 'dart:typed_data';

import 'package:flutter/foundation.dart';
import 'package:flutter/material.dart';
import 'package:opencv_dart/opencv_dart.dart' as cv;
import 'package:image_picker/image_picker.dart';

void main() {
  runApp(const MyApp());
}

class MyApp extends StatefulWidget {
  const MyApp({super.key});

  @override
  State<MyApp> createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  var images = <Uint8List>[];

  @override
  void initState() {
    super.initState();
  }

  @override
  void dispose() {
    super.dispose();
  }

  // native resources are unsendable for isolate, so use raw data or encoded Uint8List and convert back
  Future<(Uint8List, Uint8List)> heavyTask(Uint8List buffer) async =>
      Isolate.run(() {
        final im = cv.imdecode(buffer, cv.IMREAD_COLOR);
        late cv.Mat gray, blur;
        for (var i = 0; i < 1000; i++) {
          gray = cv.cvtColor(im, cv.COLOR_BGR2GRAY);
          blur = cv.gaussianBlur(im, (7, 7), 2, sigmaY: 2);
        }
        return (cv.imencode(".png", gray).$2, cv.imencode(".png", blur).$2);
      });

  Future<(cv.Mat, cv.Mat)> heavyTaskAsync(cv.Mat im) async {
    late cv.Mat gray, blur;
    for (var i = 0; i < 1000; i++) {
      gray = await cv.cvtColorAsync(im, cv.COLOR_BGR2GRAY);
      blur = await cv.gaussianBlurAsync(im, (7, 7), 2, sigmaY: 2);
    }
    return (gray, blur);
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: const Text('Native Packages'),
        ),
        body: Container(
          alignment: Alignment.center,
          child: Column(
            children: [
              ElevatedButton(
                onPressed: () async {
                  final picker = ImagePicker();
                  final img =
                      await picker.pickImage(source: ImageSource.gallery);
                  if (img != null) {
                    final path = img.path;
                    final mat = cv.imread(path);
                    print(
                        "cv.imread: width: ${mat.cols}, height: ${mat.rows}, path: $path");
                    final (success, bytes) = cv.imencode(".png", mat);
                    print("imencode: $success, ${bytes.length}");
                    // heavy computation
                    final (gray, blur) = await heavyTask(bytes);
                    setState(() {
                      images = [bytes, gray, blur];
                    });
                  }
                },
                child: const Text("Pick Image"),
              ),
              ElevatedButton(
                onPressed: () async {
                  final data = await DefaultAssetBundle.of(context)
                      .load("images/lenna.png");
                  final bytes = data.buffer.asUint8List();
                  // heavy computation
                  // final (gray, blur) = await heavyTask(bytes);
                  // setState(() {
                  //   images = [bytes, gray, blur];
                  // });
                  final (gray, blur) =
                      await heavyTaskAsync(cv.imdecode(bytes, cv.IMREAD_COLOR));
                  setState(() {
                    images = [
                      bytes,
                      cv.imencode(".png", gray).$2,
                      cv.imencode(".png", blur).$2
                    ];
                  });
                },
                child: const Text("Process"),
              ),
              Expanded(
                flex: 2,
                child: Row(
                  children: [
                    Expanded(
                      child: ListView.builder(
                        itemCount: images.length,
                        itemBuilder: (ctx, idx) => Card(
                          child: Image.memory(images[idx]),
                        ),
                      ),
                    ),
                    Expanded(
                      child: SingleChildScrollView(
                        child: Text(cv.getBuildInformation()),
                      ),
                    ),
                  ],
                ),
              ),
            ],
          ),
        ),
      ),
    );
  }
}