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The process of invoking a Cloud Function in Firebase through Flutter involves the following steps:

1. Set up your Flutter project and integrate Firebase into your app.

2. Create a Cloud Function in Firebase Console or deploy it using Firebase CLI.

3. Write a function in Flutter to call the Cloud Function. You can use the FirebaseFunctions class from the firebase_functions package and initialize it using FirebaseFunctions.instance, which returns a singleton instance. Then, you can call the Cloud Function using the httpsCallable method of the FirebaseFunctions class.

4. Pass the necessary parameters to the Cloud Function using a Map object.

5. Handle the response of the Cloud Function in your Flutter code.

Here is an example of how you can call a Cloud Function named addNumbers in Flutter:

import 'package:firebase_functions/firebase_functions.dart';

final functions = FirebaseFunctions.instance;

Future<int> addNumbers(int a, int b) async {
  final httpsCallable = functions.httpsCallable('addNumbers');
  final result = await httpsCallable.call({
    'a': a,
    'b': b,
  });
  return result.data;
}

This function takes two integers a and b as parameters, calls the Cloud Function addNumbers with these parameters, and returns the result of the Cloud Function as an integer. You can use this function in your Flutter code like this:

int result = await addNumbers(3, 4);
print(result); // prints 7

Note that you need to handle errors that may occur while calling the Cloud Function. The call method of the FirebaseFunctions.HttpsCallable class returns a HttpsCallableResult object that has a data property containing the result of the Cloud Function. However, the call method may throw an exception if the Cloud Function fails to execute. You can handle these exceptions using a try-catch block.