Trying to understand the issue. The options that you show only apply to uploaded files I though, so why have an option offline.
If you are thinking to run the site offline then surely you will have a local collection of the images and it would work as in the options.

I have people who publish topics by adding images. I often have to modify these images for the layout and for legal issues I have to keep the original images in the publication but make them invisible or inaccessible.

So a user posts an image via the site which you edit before publishing.
So you have two images?
Why do you have to keep the original image in the publication (published post) if it is not to be published, hence the editing.
How do you add the edited image? Do you access the file by ftp and edit it so the image link will just pick up on the edited version, in which case the original you must save under a different name.
Sorry not getting this ??

he publishes images that are huge 10mb while in JPG 100ko. I edit the subject and add a lighter photo

I get the editing but why do you want to keep original photo unless you want it to be accessible via a thumbnail or the edited image?

One problem is the term offline. To me this means not accessible from the internet. The blog can't decide that a file is offline only if it accessible. You could keep the images on a local computer and access it if you have it as a server, so that sometimes it is offline but then I don't see why you just don't deny access to them on the web server.

I'm clearly not getting what you mean by offline.

The idea is that the file is not visible in the publication.

You seriously need to hire a coder.

I still don't see the problem.
Presumably you edit a file and that is visible, so what do you want to do with the original? Does it still need to be accessible on the website. If not just move it to another folder [original-images]

The original file is not allowed to be deleted. I can not see myself going in FTP to change 1TB of daily files. It would be possible to endress it unreachable by modifying the CHMOD…

So you just want the uploaded files invisible.
I suppose if the files are uploaded on individual posts there are all in folders for that post.
So if you edit a files in doing so you can change the name of the original file as you edit it, so it isn't accessible

I do not have the right to change the name of the files. When a subject is non-compliant in the presentation a replacement file is sent. The original file remains in the subject. But it is not visible except in admin mode.

When you edit a file can you not just move the original it to another folder?

Sorry to be a pain :(

There are too many members and speakers and I do not have the authority to change all topics.

So do you want an option that each user can operate to a) reduce the size and 2) to hide the original
It's more to do with the image size on the publication than the space used on the server.

only hide the image, pdf…

Still struggling with this.
You just want an option for any user who uploads an image to be able to hide it so it doesn't use bandwidth, but
a) you do want to keep the file and
b) you are or want someone/somehow to be able to edit the image and show that.

Generally if a user uploads an image it goes in the quick-uploads folder in /media//
So if you edit an image you can place it there.

I;ve never tried but will have a look at doing that. My idea is to just replace the file with the edited one which should then be the one the sever sends to the client. The original will just have a prefix..

But this is much as I said before.

Not much help hey! :(

@nospy if you only need to hide the image you can set it to "online" but not reference it in the post. This way it will not appear anywhere but the backoffice.

If you need more permission/access management on files, that will require developing some custom code for you indeed.