getImage method
Implementation
Future<Image?> getImage({int page = 1}) async {
assert(page > 0);
if (_imagePreloaded && images![page - 1] != null) return images![page - 1];
var data = await _channel.invokeMethod('getPage', {'filePath': _filePath, 'pageNumber': page});
return new Image.file(File(data));
}