added processCameraImage function

lib/flutter_zxing.dart

@@ -1,6 +1,7 @@
 import 'dart:async';
 import 'dart:ffi';
 import 'dart:io';
+import 'dart:isolate';
 import 'dart:typed_data';
 
 import 'package:camera/camera.dart';
@@ -10,6 +11,7 @@ import 'package:flutter/services.dart';
 import 'package:image/image.dart' as imglib;
 
 import 'generated_bindings.dart';
+import 'isolate_utils.dart';
 
 export 'generated_bindings.dart';
 export 'reader_widget.dart';
@@ -17,6 +19,7 @@ export 'writer_widget.dart';
 export 'image_converter.dart';
 export 'scanner_overlay.dart';
 
+/// The main class for reading barcodes from images or camera.
 class FlutterZxing {
   static const MethodChannel _channel = MethodChannel('flutter_zxing');
 
@@ -27,6 +30,8 @@ class FlutterZxing {
 
   static final bindings = GeneratedBindings(dylib);
 
+  static IsolateUtils? isolateUtils;
+
   static bool logEnabled = false;
 
   static void setLogEnabled(bool enabled) {
@@ -36,6 +41,16 @@ class FlutterZxing {
   /// Returns a version of the zxing library
   static String version() => bindings.version().cast<Utf8>().toDartString();
 
+  /// Starts reading barcode from the camera
+  static Future startCameraProcessing() async {
+    // Spawn a new isolate
+    isolateUtils = IsolateUtils();
+    await isolateUtils?.startReadingBarcode();
+  }
+
+  /// Stops reading barcode from the camera
+  static stopCameraProcessing() => isolateUtils?.stopReadingBarcode();
+
   /// Reads barcode from String image path
   static Future<CodeResult?> readImagePathString(
     String path, {
@@ -114,7 +129,25 @@ class FlutterZxing {
     return result;
   }
 
-  static int get _logEnabled => logEnabled ? 1 : 0;
+  static Future<CodeResult> processCameraImage(
+      CameraImage image, int format, double cropPercent) async {
+    var isolateData = IsolateData(image, format, cropPercent);
+    CodeResult result = await _inference(isolateData);
+    return result;
+  }
+
+  /// Runs inference in another isolate
+  static Future<CodeResult> _inference(IsolateData isolateData) async {
+    ReceivePort responsePort = ReceivePort();
+    isolateUtils?.sendPort
+        ?.send(isolateData..responsePort = responsePort.sendPort);
+    var results = await responsePort.first;
+    return results;
+  }
+
+  static int get _logEnabled {
+    return logEnabled ? 1 : 0;
+  }
 
   static String formatName(int format) => _formatNames[format] ?? 'Unknown';
 }

lib/isolate_utils.dart

@@ -33,9 +33,9 @@ class IsolateUtils {
 
   SendPort? get sendPort => _sendPort;
 
-  Future<void> start() async {
+  Future<void> startReadingBarcode() async {
     _isolate = await Isolate.spawn<SendPort>(
-      entryPoint,
+      readBarcodeEntryPoint,
       _receivePort.sendPort,
       debugName: kDebugName,
     );
@@ -43,13 +43,13 @@ class IsolateUtils {
     _sendPort = await _receivePort.first;
   }
 
-  void stop() {
+  void stopReadingBarcode() {
     _isolate?.kill(priority: Isolate.immediate);
     _isolate = null;
     _sendPort = null;
   }
 
-  static void entryPoint(SendPort sendPort) async {
+  static void readBarcodeEntryPoint(SendPort sendPort) async {
     final port = ReceivePort();
     sendPort.send(port.sendPort);
 
@@ -66,7 +66,7 @@ class IsolateUtils {
               image.width, image.height, cropSize, cropSize);
 
           isolateData.responsePort?.send(result);
-        } on Exception catch (e) {
+        } catch (e) {
           isolateData.responsePort?.send(e);
         }
       }

lib/reader_widget.dart

@@ -1,6 +1,5 @@
 import 'dart:async';
 import 'dart:io';
-import 'dart:isolate';
 import 'dart:math';
 
 import 'package:camera/camera.dart';
@@ -60,8 +59,7 @@ class _ReaderWidgetState extends State<ReaderWidget>
 
   void initStateAsync() async {
     // Spawn a new isolate
-    isolateUtils = IsolateUtils();
-    await isolateUtils?.start();
+    await FlutterZxing.startCameraProcessing();
 
     availableCameras().then((cameras) {
       setState(() {
@@ -94,8 +92,8 @@ class _ReaderWidgetState extends State<ReaderWidget>
 
   @override
   void dispose() {
+    FlutterZxing.stopCameraProcessing();
     controller?.dispose();
-    isolateUtils?.stop();
     super.dispose();
   }
 
@@ -116,7 +114,7 @@ class _ReaderWidgetState extends State<ReaderWidget>
       await controller?.initialize();
       controller?.startImageStream(processCameraImage);
     } on CameraException catch (e) {
-      _showCameraException(e);
+      debugPrint('${e.code}: ${e.description}');
     }
 
     controller?.addListener(() {
@@ -131,30 +129,15 @@ class _ReaderWidgetState extends State<ReaderWidget>
     widget.onControllerCreated?.call(controller);
   }
 
-  void _showCameraException(CameraException e) {
-    logError(e.code, e.description);
-    showInSnackBar('Error: ${e.code}\n${e.description}');
-  }
-
-  void showInSnackBar(String message) {}
-
-  void logError(String code, String? message) {
-    if (message != null) {
-      debugPrint('Error: $code\nError Message: $message');
-    } else {
-      debugPrint('Error: $code');
-    }
-  }
-
   processCameraImage(CameraImage image) async {
     if (!_isProcessing) {
       _isProcessing = true;
       try {
-        var isolateData =
-            IsolateData(image, widget.codeFormat, widget.cropPercent);
-
-        /// perform inference in separate isolate
-        CodeResult result = await inference(isolateData);
+        CodeResult result = await FlutterZxing.processCameraImage(
+          image,
+          widget.codeFormat,
+          widget.cropPercent,
+        );
         if (result.isValidBool) {
           if (widget.beep) {
             FlutterBeep.beep();
@@ -175,15 +158,6 @@ class _ReaderWidgetState extends State<ReaderWidget>
     return null;
   }
 
-  /// Runs inference in another isolate
-  Future<CodeResult> inference(IsolateData isolateData) async {
-    ReceivePort responsePort = ReceivePort();
-    isolateUtils?.sendPort
-        ?.send(isolateData..responsePort = responsePort.sendPort);
-    var results = await responsePort.first;
-    return results;
-  }
-
   @override
   Widget build(BuildContext context) {
     final size = MediaQuery.of(context).size;