Outpainting

Outpainting generates what might lie beyond an image's borders. Turning a square photo into a wide header is its most common use.

Its practical value is reusing one image at different aspect ratios: taking an Instagram post to story dimensions, or a product shot to a wide banner.

Its limit: the model does not know what was outside the frame, it guesses. If a decisive detail falls into the extended area — a person's body, the continuation of a building — the result may not convince.