1. An information processing apparatus comprising: at least one processor for causing the information processing apparatus to: acquire an input image having one or more pixels and, for each pixel of the input image, positional information of at least an object in the acquired input image and a surface in the acquired input image in a space including the surface as part of a background; and extract from the acquired input image, in an a first area including the surface in the background, an a first object area corresponding to an the object existing in the a foreground with respect to the surface, based on the positional information of the object in the acquired input image, the positional information of the surface, and a first reference, and to extract from the acquired input image, in a second area not including the surface in the background, an a second object area corresponding to the object existing in the foreground with respect to the surface, based on the positional information of the object in the acquired input image, and a second reference different from the first reference.