There are two kinds. Shopper-facing try-on puts clothes on the shopper's own photo or camera image. Seller-side try-on, as in Herofab, dresses a model in the garment from a product photo, to produce listing images.
Because the person in the image is generated, disclosure rules apply: the EU AI Act requires synthetic images to be marked in a machine-readable way, and Herofab embeds that marker in every image.