I think you misunderstand.
I think your procedure produces a UV map template image.
In the screen-shot you posted, suppose I want to put eyes on that blob that looks like a head.
To do so, I would make an image of eyes, and as I make this image of the eyes, I would position the eyes using the template UV map.
Now, somehow, the Blender file for the head-blob also contains the eye-image file that it projects on to the surface according to the UV template map image.
[Unfortunately, I do not know the process by which Blender users make and apply such images such the eye-image that I’m talking about, because I’ve never done this procedure in Blender myself.]
But anyway, what I want to do is extract the eye-mage file from the .blend file, the image that shows the eyes, NOT the UV map template used to locate the eyes on the head when making that eye-image file.
Wait. That’s not just a screenshot. That’s a tutorial movie clip. Let me examine the movie clip first. Maybe the answer is there.
Yup. It worked for me. Thanks, Hunkadoodle!