1. An image processing apparatus, comprising: at least one processor configured to: perform an inter-magnification-ratio blur-compensation prediction with respect to a reduced-size reference focus face image, to thereby generate an inter-magnification-ratio blur-compensation predicted image at each of a plurality of focus positions, the reduced-size reference focus face image being obtained by reducing a size of a reference focus face image to be a reference of a plurality of focus face images obtained by imaging a subject at the plurality of focus positions, wherein the inter-magnification-ratio blur-compensation prediction is performed using a magnification filter followed by a blur compensation filter, wherein the magnification filter is a Lanczos filter, and wherein the blur compensation filter used for each of the plurality of focus positions is a point spread function of the respective focus position; generate, for each of the plurality of focus positions, differential data between the focus face image associated with a respective focus position and the inter-magnification-ratio blur-compensation predicted image associated with the same respective focus position; and encode the reduced-size reference focus face image and the generated differential data.