Restricting /assets to non logged in users

Good evening,

I have been using Codeigniter 4 for some time now and I am very happy with it!
I have recently noticed the following problem, so I am asking for your advice:

I have pictures in the /assets/Pictures directory which have to be there so that they can be loaded in a HTML page with a <img>-tag.
But these pictures should only be visible for users who are logged in to my site.
Is there a way to restrict the images this way?
If I move them to another directory outside the assets folder, I can't see them anymore with <img>.

I would be very grateful for any help!

Have a nice evening,
Paul