An image view displays a single image or an animated sequence of images over a transparent or opaque background. Within an image view, images may be stretched, scaled, sized to fit, or pinned to a specific location. Image views are noninteractive by default.
If possible, make sure all images in an animated sequence are consistently sized. Ideally, images should be prescaled to fit the view so the system doesn't have to do any scaling. If the system must perform scaling, it's easiest to achieve the desired results when all images are the same size and shape.
For developer guidance, see UIImageView.