Add image copy functionality.

Currently only supports Windows.
Close #260

lib/pages/reader/comic_image.dart

@@ -24,6 +24,8 @@ class ComicImage extends StatefulWidget {
     Map<String, String>? headers,
     int? cacheWidth,
     int? cacheHeight,
+    this.onInit,
+    this.onDispose,
   })  : image = ResizeImage.resizeIfNeeded(cacheWidth, cacheHeight, image),
         assert(cacheWidth == null || cacheWidth > 0),
         assert(cacheHeight == null || cacheHeight > 0);
@@ -60,6 +62,10 @@ class ComicImage extends StatefulWidget {
 
   final bool isAntiAlias;
 
+  final void Function(State<ComicImage> state)? onInit;
+
+  final void Function(State<ComicImage> state)? onDispose;
+
   static void clear() => _ComicImageState.clear();
 
   @override
@@ -87,6 +93,7 @@ class _ComicImageState extends State<ComicImage> with WidgetsBindingObserver {
     super.initState();
     WidgetsBinding.instance.addObserver(this);
     _scrollAwareContext = DisposableBuildContext<State<ComicImage>>(this);
+    widget.onInit?.call(this);
   }
 
   @override
@@ -97,6 +104,7 @@ class _ComicImageState extends State<ComicImage> with WidgetsBindingObserver {
     _completerHandle?.dispose();
     _scrollAwareContext.dispose();
     _replaceImage(info: null);
+    widget.onDispose?.call(this);
     super.dispose();
   }
 
@@ -136,6 +144,15 @@ class _ComicImageState extends State<ComicImage> with WidgetsBindingObserver {
     super.reassemble();
   }
 
+  bool containsPoint(Offset point) {
+    if (!mounted) {
+      return false;
+    }
+    var renderBox = context.findRenderObject() as RenderBox;
+    var localPoint = renderBox.globalToLocal(point);
+    return renderBox.paintBounds.contains(localPoint);
+  }
+
   void _updateInvertColors() {
     _invertColors = MediaQuery.maybeInvertColorsOf(context) ??
         SemanticsBinding.instance.accessibilityFeatures.invertColors;

lib/pages/reader/gesture.dart

@@ -281,6 +281,12 @@ class _ReaderGestureDetectorState extends AutomaticGlobalState<_ReaderGestureDet
             context.pop();
           },
         ),
+        if (App.isDesktop && !reader.isLoading)
+          MenuEntry(
+            icon: Icons.copy,
+            text: "Copy Image".tl,
+            onClick: () => copyImage(location),
+          ),
       ],
     );
   }
@@ -303,6 +309,16 @@ class _ReaderGestureDetectorState extends AutomaticGlobalState<_ReaderGestureDet
 
   @override
   Object? get key => "reader_gesture";
+
+  void copyImage(Offset location) async {
+    var controller = reader._imageViewController;
+    var image = await controller!.getImageByOffset(location);
+    if (image != null) {
+      writeImageToClipboard(image);
+    } else {
+      context.showMessage(message: "No Image");
+    }
+  }
 }
 
 class _DragListener {

lib/pages/reader/images.dart

@@ -113,6 +113,8 @@ class _GalleryModeState extends State<_GalleryMode>
 
   int get totalPages => (reader.images!.length / reader.imagesPerPage).ceil();
 
+  var imageStates = <State<ComicImage>>{};
+
   @override
   void initState() {
     reader = context.reader;
@@ -234,6 +236,8 @@ class _GalleryModeState extends State<_GalleryMode>
         child: ComicImage(
           image: imageProvider,
           fit: BoxFit.contain,
+          onInit: (state) => imageStates.add(state),
+          onDispose: (state) => imageStates.remove(state),
         ),
       );
     }).toList();
@@ -370,6 +374,28 @@ class _GalleryModeState extends State<_GalleryMode>
   bool handleOnTap(Offset location) {
     return false;
   }
+
+  @override
+  Future<Uint8List?> getImageByOffset(Offset offset) async {
+    String? imageKey;
+    if (reader.imagesPerPage == 1) {
+      imageKey = reader.images![reader.page - 1];
+    } else {
+      for (var imageState in imageStates) {
+        if ((imageState as _ComicImageState).containsPoint(offset)) {
+          imageKey = (imageState.widget.image as ReaderImageProvider).imageKey;
+        }
+      }
+    }
+    if (imageKey == null) return null;
+    if (imageKey.startsWith("file://")) {
+      return await File(imageKey.substring(7)).readAsBytes();
+    } else {
+      return (await CacheManager().findCache(
+              "$imageKey@${context.reader.type.sourceKey}@${context.reader.cid}@${context.reader.eid}"))!
+          .readAsBytes();
+    }
+  }
 }
 
 const Set<PointerDeviceKind> _kTouchLikeDeviceTypes = <PointerDeviceKind>{
@@ -414,6 +440,8 @@ class _ContinuousModeState extends State<_ContinuousMode>
   /// To handle the tap event, we need to know if the user was scrolling before the delay.
   bool delayedIsScrolling = false;
 
+  var imageStates = <State<ComicImage>>{};
+
   void delayedSetIsScrolling(bool value) {
     Future.delayed(
       const Duration(milliseconds: 300),
@@ -574,6 +602,8 @@ class _ContinuousModeState extends State<_ContinuousMode>
             width: width,
             height: height,
             fit: BoxFit.contain,
+            onInit: (state) => imageStates.add(state),
+            onDispose: (state) => imageStates.remove(state),
           ),
         );
       },
@@ -857,6 +887,24 @@ class _ContinuousModeState extends State<_ContinuousMode>
     }
     return false;
   }
+
+  @override
+  Future<Uint8List?> getImageByOffset(Offset offset) async {
+    String? imageKey;
+    for (var imageState in imageStates) {
+      if ((imageState as _ComicImageState).containsPoint(offset)) {
+        imageKey = (imageState.widget.image as ReaderImageProvider).imageKey;
+      }
+    }
+    if (imageKey == null) return null;
+    if (imageKey.startsWith("file://")) {
+      return await File(imageKey.substring(7)).readAsBytes();
+    } else {
+      return (await CacheManager().findCache(
+              "$imageKey@${context.reader.type.sourceKey}@${context.reader.cid}@${context.reader.eid}"))!
+          .readAsBytes();
+    }
+  }
 }
 
 ImageProvider _createImageProviderFromKey(

lib/pages/reader/reader.dart

@@ -30,6 +30,7 @@ import 'package:venera/foundation/local.dart';
 import 'package:venera/foundation/log.dart';
 import 'package:venera/foundation/res.dart';
 import 'package:venera/pages/settings/settings_page.dart';
+import 'package:venera/utils/clipboard_image.dart';
 import 'package:venera/utils/data_sync.dart';
 import 'package:venera/utils/ext.dart';
 import 'package:venera/utils/file_type.dart';
@@ -577,4 +578,6 @@ abstract interface class _ImageViewController {
 
   /// Returns true if the event is handled.
   bool handleOnTap(Offset location);
+
+  Future<Uint8List?> getImageByOffset(Offset offset);
 }