How to search for and connect to a scanner in flutter windows app?

Question

Iam trying to make a flutter windows application that can connect to a scanner device and get the image data from it, but i can't seem to find any packages that help with that so if anyone can give me the link of a library or a tutorial that can help with that. Thanks in advance.

i have tried searching but all the packages i have found are directed to android and ios only.

Answer 1

Is this what you want?

I've ported the C++ code from https://github.com/twain/twain-samples and created an open source project https://github.com/yushulx/flutter_twain_scanner.

The plugin is available on https://pub.dev/packages/flutter_twain_scanner

The full code to scan documents from a connected scanner on Windows desktop:

import 'dart:io';

import 'package:flutter/material.dart';
import 'dart:async';

import 'package:flutter/services.dart';
import 'package:flutter_twain_scanner/flutter_twain_scanner.dart';

import 'dart:ui' as ui;

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

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

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

class _MyAppState extends State<MyApp> {
  String _platformVersion = 'Unknown';
  final _flutterTwainScannerPlugin = FlutterTwainScanner();
  String? _documentPath;
  List<String> _scanners = []; // Option 2
  String? _selectedScanner;

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

  // Platform messages are asynchronous, so we initialize in an async method.
  Future<void> initPlatformState() async {
    String platformVersion;
    // Platform messages may fail, so we use a try/catch PlatformException.
    // We also handle the message potentially returning null.
    try {
      platformVersion = await _flutterTwainScannerPlugin.getPlatformVersion() ??
          'Unknown platform version';
    } on PlatformException {
      platformVersion = 'Failed to get platform version.';
    }

    // If the widget was removed from the tree while the asynchronous platform
    // message was in flight, we want to discard the reply rather than calling
    // setState to update our non-existent appearance.
    if (!mounted) return;

    setState(() {
      _platformVersion = platformVersion;
    });
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: const Text('Flutter TWAIN Scanner'),
        ),
        body: Stack(
          children: <Widget>[
            Column(
              mainAxisAlignment: MainAxisAlignment.start,
              children: [
                SizedBox(
                  height: 100,
                  child: Row(
                      mainAxisAlignment: MainAxisAlignment.spaceEvenly,
                      children: <Widget>[
                        MaterialButton(
                            textColor: Colors.white,
                            color: Colors.blue,
                            onPressed: () async {
                              List<String>? scanners =
                                  await _flutterTwainScannerPlugin
                                      .getDataSources();

                              if (scanners != null) {
                                setState(() {
                                  _scanners = scanners;
                                });
                              }
                            },
                            child: const Text('List Scanners')),
                        DropdownButton(
                          hint: Text(
                              'Select a scanner'), // Not necessary for Option 1
                          value: _selectedScanner,
                          onChanged: (newValue) {
                            setState(() {
                              _selectedScanner = newValue;
                            });
                          },
                          items: _scanners.map((location) {
                            return DropdownMenuItem(
                              child: new Text(location),
                              value: location,
                            );
                          }).toList(),
                        ),
                        MaterialButton(
                            textColor: Colors.white,
                            color: Colors.blue,
                            onPressed: () async {
                              if (_selectedScanner != null) {
                                int index =
                                    _scanners.indexOf(_selectedScanner!);
                                String? documentPath =
                                    await _flutterTwainScannerPlugin
                                        .scanDocument(index);
                                setState(() {
                                  _documentPath = documentPath;
                                });
                              }
                            },
                            child: const Text('Scan Document')),
                      ]),
                ),
                SizedBox(
                    height: 600,
                    child: SingleChildScrollView(
                      scrollDirection: Axis.vertical,
                      child: _documentPath == null
                          ? Image.asset('images/default.png')
                          : Image.file(
                              File(_documentPath!),
                              fit: BoxFit.contain,
                              width: 600,
                              height: 600,
                            ),
                    ))
              ],
            ),
          ],
        ),
      ),
    );
  }
}