With ChatGPTs API I've built a small module that renders a small button sitting next to image's description field that when clicked does image recognition of the image, and spits out a small text for alt purposes. The irony? The real value of this would be the actual automation which I haven't had time to do hahaha.
Also I have to mention it works fairly well, but would like to make it more "on brand" when doing the prompts, so I gotta work on an interface to kinda make this presets?? So that the final description is based on something related not just purely descriptive (in come cases). I haven't had time to do some trial/error. But for now it kinda works like the site you pasted!