The replaced content is sized to maintain its aspect ratio while fitting within the element's content box: its concrete object size is resolved as a contain constraint against the element's used width and height.

The replaced content is sized to maintain its aspect ratio while filling the element's entire content box: its concrete object size is resolved as a cover constraint against the element's used width and height.

The replaced content is sized to fill the element's content box: the object's concrete object size is the element's used width and height.

The replaced content is not resized to fit inside the element's content box: determine the object's concrete object size using the default sizing algorithm with no specified size, and a default object size equal to the replaced element's used width and height.

Size the content as if none or contain were specified, whichever would result in a smaller concrete object size.