1. A catalog image generation apparatus comprising: image generation means for generating, from image data representing an image, a reference shadow image wherein a main subject of the image has a reference shadow lightness, a reference highlight image wherein the main subject has a reference highlight lightness, and a desired lightness image wherein the main subject has a desired lightness, and for generating from the image data at least one first intermediate lightness image having lightness that is appropriately perceived by human vision to evenly divide the lightness between the reference shadow image and the desired lightness image, and at least one second intermediate lightness image having lightness that is appropriately perceived by human vision to evenly divide the lightness between the reference highlight image and the desired lightness image; and catalog image generation means for generating a catalog image in which the reference shadow image, the at least one first intermediate lightness image, the desired lightness image, the at least one second intermediate lightness image, and the reference highlight image are arranged.