Read image file from iOS local storage and display in an image widget?

I have tried using the whole image path from the Firebase collection field which didn't work and also when reading the file and also by using the following code by just including the name of the file as an input string.

import 'dart:io';
import 'package:path_provider/path_provider.dart';

Future<String> readFromFolder(String shortname) async {

  shortname = shortname + '.png';

  // Get the directory for the app's documents
  Directory appDocDir = await getApplicationDocumentsDirectory();

  // Construct the full path to the image file
  String filePath = '${appDocDir.path}/images/$shortname)';

  // Check if the file exists
  if (await File(filePath).exists()) {
    // Read the file and return its contents
    return await File(filePath).readAsString();
  } else {
    throw Exception('File not found');
  }
}

but it is giving a File not found message