Can embedded photo be retained after deleting from library?

Simple answer: yes.

Geekier answer: That would be true for most types of documents. (I would say all documents, but there may have been historic exceptions. Read on.)

There have been technologies in Mac history that allowed document processors to keep track of updates in the source of segments of the documents they manage (picking up edits, for example), but I don't think any of them are still active. (Apple had "Publish and Subscribe" way back in Mac OS 7, but I'm not sure that it would notice a deleted source photo and remove the copy embedded in a document. It has been gone for decades.)

I don't know of any consumer-grade word or document processors that attempt such tricks these days.

Which kind of document is it? If you used your photos in a document created by a word processor or presentation software, the the photo may have become downsized to fit into the place holders and not stored in the full resolution. Then you can only recover it at a lower resolution.

I just tested to recover some photos from a Pages document.when I open a Pages document with embedded photos I can select a photo on a Pageant copy it to the clipboard, then open the Preview.app and use the command "File > New from Clipboard" and create a new image from the copied image and export it as a file, then import this file back to Photos.

Good question, Richard. When I tested it, the copied photo had the same resolution as the photo shown on the Pages page. Pretty good, because I am inserting photos a full-page photos.

In Keynote documents and old PowerPoint documents I can extract the photos again by ctrl-clicking the document in the Finder and using Show Package content. The images and videos are embedded in the full resolution. But this does not work for Pages documents.

markwmsn is absolutely right. In the way-back past I've wondered this, too, but it's certainly not happened in the past ten (twenty?) years!

But, hey-- why not just try it? Delete a picture from the Library (but don't remove it from Recently Deleted!) Then see what happens to your document.

When a picture is in Recently Deleted, or a document is in the Trash, it can't be used by any app, but it can be restored. Go ahead and convince yourself that it's OK.

léonie wrote:

….The images and videos are embedded in the full resolution. But this does not work for Pages documents.

Use the command line to unzip the pages.container, access the container zip contents, and see if media-specific files are maintained there? (i don’t currently have access to a Mac.)

léonie wrote: …I just tested to recover some photos from a Pages document. … copy it to the clipboard, then open the Preview.app and use the command "File > New from Clipboard" and create a new image from the copied image and export it as a file, then import this file back to Photos.

Did the picture arrive back with the same resolution and quality?

I have some old Word documents that seem to have lost the pictures--there is sometimes a complaint about too much memory or something. I'm thinking such documents would be poor places to depend on for storing pictures.

Perhaps we can help better, if we know, what the problem is you want to fix. Has your Photos Library become damaged and can no longer be opened or are photos missing? Or do you just want to remove clutter from your Photos Library?