fix #107

lib/foundation/appdata.dart

@@ -13,7 +13,7 @@ class _Appdata {
 
   bool _isSavingData = false;
 
-  Future<void> saveData() async {
+  Future<void> saveData([bool sync = true]) async {
     if (_isSavingData) {
       await Future.doWhile(() async {
         await Future.delayed(const Duration(milliseconds: 20));
@@ -25,7 +25,9 @@ class _Appdata {
     var file = File(FilePath.join(App.dataPath, 'appdata.json'));
     await file.writeAsString(data);
     _isSavingData = false;
-    DataSync().uploadData();
+    if (sync) {
+      DataSync().uploadData();
+    }
   }
 
   void addSearchHistory(String keyword) {
@@ -78,6 +80,25 @@ class _Appdata {
     };
   }
 
+  /// Following fields are related to device-specific data and should not be synced.
+  static const _disableSync = [
+    "proxy",
+    "authorizationRequired",
+    "customImageProcessing",
+  ];
+
+  /// Sync data from another device
+  void syncData(Map<String, dynamic> data) {
+    for (var key in data.keys) {
+      if (_disableSync.contains(key)) {
+        continue;
+      }
+      settings[key] = data[key];
+    }
+    searchHistory = List.from(data['searchHistory']);
+    saveData();
+  }
+
   var implicitData = <String, dynamic>{};
 
   void writeImplicitData() {
@@ -126,6 +147,8 @@ class _Settings with ChangeNotifier {
     'onClickFavorite': 'viewDetail', // viewDetail, read
     'enableDnsOverrides': false,
     'dnsOverrides': {},
+    'enableCustomImageProcessing': false,
+    'customImageProcessing': _defaultCustomImageProcessing,
   };
 
   operator [](String key) {
@@ -142,3 +165,16 @@ class _Settings with ChangeNotifier {
     return _data.toString();
   }
 }
+
+const _defaultCustomImageProcessing = '''
+/**
+ * Process an image
+ * @param image {ArayBuffer} - The image to process
+ * @param cid {string} - The comic ID
+ * @param eid {string} - The episode ID
+ * @returns {Promise<ArrayBuffer>} - The processed image
+ */
+async function processImage(image, cid, eid) {
+    return image;
+}
+''';

lib/foundation/image_provider/reader_image.dart

@@ -1,10 +1,13 @@
 import 'dart:async' show Future, StreamController;
 import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
+import 'package:flutter_qjs/flutter_qjs.dart';
+import 'package:venera/foundation/js_engine.dart';
 import 'package:venera/network/images.dart';
 import 'package:venera/utils/io.dart';
 import 'base_image_provider.dart';
 import 'reader_image.dart' as image_provider;
+import 'package:venera/foundation/appdata.dart';
 
 class ReaderImageProvider
     extends BaseImageProvider<image_provider.ReaderImageProvider> {
@@ -21,25 +24,50 @@ class ReaderImageProvider
 
   @override
   Future<Uint8List> load(StreamController<ImageChunkEvent> chunkEvents) async {
+    Uint8List? imageBytes;
     if (imageKey.startsWith('file://')) {
       var file = File(imageKey);
       if (await file.exists()) {
-        return file.readAsBytes();
+        imageBytes = await file.readAsBytes();
+      } else {
+        throw "Error: File not found.";
       }
-      throw "Error: File not found.";
-    }
-
-    await for (var event
+    } else {
+      await for (var event
         in ImageDownloader.loadComicImage(imageKey, sourceKey, cid, eid)) {
-      chunkEvents.add(ImageChunkEvent(
-        cumulativeBytesLoaded: event.currentBytes,
-        expectedTotalBytes: event.totalBytes,
-      ));
-      if (event.imageBytes != null) {
-        return event.imageBytes!;
+        chunkEvents.add(ImageChunkEvent(
+          cumulativeBytesLoaded: event.currentBytes,
+          expectedTotalBytes: event.totalBytes,
+        ));
+        if (event.imageBytes != null) {
+          imageBytes = event.imageBytes;
+          break;
+        }
       }
     }
-    throw "Error: Empty response body.";
+    if (imageBytes == null) {
+      throw "Error: Empty response body.";
+    }
+    if (appdata.settings['enableCustomImageProcessing']) {
+      var script = appdata.settings['customImageProcessing'].toString();
+      if (!script.contains('async function processImage')) {
+        return imageBytes;
+      }
+      var func = JsEngine().runCode('''
+        (() => {
+          $script
+          return processImage;
+        })()
+      ''');
+      if (func is JSInvokable) {
+        var result = await func.invoke([imageBytes, cid, eid]);
+        func.free();
+        if (result is Uint8List) {
+          return result;
+        }
+      }
+    }
+    return imageBytes;
   }
 
   @override