extracticondart.cpp

        else if (method_name.compare("iconToBytes") == 0)
        {
            const flutter::EncodableMap &args = std::get<flutter::EncodableMap>(*method_call.arguments());
            std::string iconLocation = std::get<std::string>(args.at(flutter::EncodableValue("iconLocation")));
            int iconID = std::get<int>(args.at(flutter::EncodableValue("iconID")));
            std::wstring iconLocationW = Encoding::Utf8ToWide(iconLocation);
            HICON icon = getIconFromFile((LPWSTR)iconLocationW.c_str(), iconID);

            std::vector<CHAR> buff;
            bool resultIcon = GetIconData(icon, 32, buff);
            if (!resultIcon)
            {
                buff.clear();
                resultIcon = GetIconData(icon, 24, buff);
            }
            std::vector<uint8_t> buff_uint8;
            for (auto i : buff)
            {
                buff_uint8.push_back(i);
            }
            result->Success(flutter::EncodableValue(buff_uint8));
        }
        else if (method_name.compare("getWindowIcon") == 0)
        {
            const flutter::EncodableMap &args = std::get<flutter::EncodableMap>(*method_call.arguments());
            int hWND = std::get<int>(args.at(flutter::EncodableValue("hWnd")));

            LRESULT iconResult = SendMessage((HWND)((LONG_PTR)hWND), WM_GETICON, 2, 0); // ICON_SMALL2 - User Made Apps
            if (iconResult == 0)
                iconResult = GetClassLongPtr((HWND)((LONG_PTR)hWND), -14); // GCLP_HICON - Microsoft Win Apps
            if (iconResult != 0)
            {

                HICON icon = (HICON)iconResult;
                std::vector<CHAR> buff;
                bool resultIcon = GetIconData(icon, 32, buff);
                if (!resultIcon)
                {
                    buff.clear();
                    resultIcon = GetIconData(icon, 24, buff);
                }
                if (resultIcon)
                {
                    std::vector<uint8_t> buff_uint8;
                    for (auto i : buff)
                    {
                        buff_uint8.push_back(i);
                    }
                    result->Success(flutter::EncodableValue(buff_uint8));
                }
                else
                {
                    std::vector<uint8_t> iconBytes;
                    iconBytes.push_back(204);
                    iconBytes.push_back(204);
                    iconBytes.push_back(204);
                    result->Success(flutter::EncodableValue(iconBytes));
                }
            }
            else
            {

                std::vector<uint8_t> iconBytes;
                iconBytes.push_back(204);
                iconBytes.push_back(204);
                iconBytes.push_back(204);
                result->Success(flutter::EncodableValue(iconBytes));
            }
        }
        else if (method_name.compare("getIconPng") == 0)
        {
            const flutter::EncodableMap &args = std::get<flutter::EncodableMap>(*method_call.arguments());
            int hIcon = std::get<int>(args.at(flutter::EncodableValue("hIcon")));
            std::vector<CHAR> buff;
            bool resultIcon = GetIconData((HICON)((LONG_PTR)hIcon), 32, buff);
            if (!resultIcon)
            {
                buff.clear();
                resultIcon = GetIconData((HICON)((LONG_PTR)hIcon), 24, buff);
            }
            if (resultIcon)
            {
                std::vector<uint8_t> buff_uint8;
                for (auto i : buff)
                {
                    buff_uint8.push_back(i);
                }
                result->Success(flutter::EncodableValue(buff_uint8));
            }
            else
            {
                std::vector<uint8_t> iconBytes;
                iconBytes.push_back(204);
                iconBytes.push_back(204);
                iconBytes.push_back(204);
                result->Success(flutter::EncodableValue(iconBytes));
            }
        }

method.dart

Map<String, Uint8List> ___kCacheIcons = <String, Uint8List>{};
Future<Uint8List?> nativeIconToBytes(String iconLocation, {int iconID = 0}) async {
  if (___kCacheIcons.containsKey(iconLocation) && iconID == 0) return ___kCacheIcons[iconLocation];
  final Map<String, dynamic> arguments = <String, dynamic>{'iconLocation': iconLocation, 'iconID': iconID};
  final Uint8List? result = await _methodChannel.invokeMethod<Uint8List>('iconToBytes', arguments);
  ___kCacheIcons[iconLocation] = result!;
  return result;
}

Future<Uint8List?> getExecutableIcon(String iconlocation, {int iconID = 0}) async {
  return nativeIconToBytes(iconlocation, iconID: iconID);
}

Future<Uint8List?> getWindowIcon(int hWnd) async {
  final Map<String, dynamic> arguments = <String, dynamic>{'hWnd': hWnd};
  final Uint8List? result = await _methodChannel.invokeMethod<Uint8List>('getWindowIcon', arguments);
  return result;
}

Future<Uint8List?> getIconPng(int hIcon) async {
  final Map<String, dynamic> arguments = <String, dynamic>{'hIcon': hIcon};
  final Uint8List? result = await _methodChannel.invokeMethod<Uint8List>('getIconPng', arguments);
  return result;
}