import 'package:metadata/metadata.dart';

    import 'package:metadata/metadata.dart';
    

    var file = "path_to_pre_existing_image_file/image.jpg";
    var bytes = File(file).readAsBytesSync();
    

    import 'package:flutter/services.dart' show ByteData, rootBundle;
    
    /* Your awesome code here */
    
    ByteData data = await rootBundle.load("assets/path_to_pre_existing_image_file/image.jpg";);
    var bytes = data.buffer.asUint8List(data.offsetInBytes, data.lengthInBytes);
    

    var result = MetaData.exifData(bytes);
    if (result.error == null) {
      var content = result.exifData; // exif data is available in contents
      saveFile(image_name, content);
    } else {
      print('File: $image.jpg, Error: ${result.error}');
    }
    

    MetaData.exifData(bytes, onValue: (CallBack result) {
      if (result.error == null) {
        var content = result.exifData;
        saveFile(image_name, content);
      } else {
        print('File: $image.jpg, Error: ${result.error}');
      }
    });
    

    var mapResult = MetaData.extractXMP(bytes);
    print(mapResult.toString());
    saveFile(image_name, mapResult);
    

      void saveFile(String fileName, dynamic exifContent) {
          File('${path}$fileName.json').writeAsStringSync(jsonEncode(exifContent));
      }