fix #107

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