1. An image processing apparatus comprising: subject region detection means for detecting regions of subjects included in an input image; cropped region setting means for setting a region including all of the regions of the subjects detected by the subject region detection means as a cropped region; expansion region addition means for adding an expansion region to expand an end of the cropped region only by a predetermined width; cutting means for cutting a cut image formed from a cut region including the cropped region and the expansion region from the input image; subject adaptation size changing means for changing a size of an image formed from the cut region by deleting a region where an influence on the subjects is small in the cut image; and entire image size changing means for changing the size of the entire image changed in size by the subject adaptation size changing means at a predetermined ratio.