1. An image display controlling apparatus including a processor and a memory, comprising: image-data maintaining means for maintaining a plurality of image data; link management means for managing a link representing a parent-child relationship of parent image data and child image data between two image data in the plurality of image data; operation receiving means for receiving operation input relating to a display of the plurality of image data; and a display controller for controlling such that switching is performed between a whole display in which all of the plurality of image data is subject to be displayed and a digest display in which image data other than those which are the child image data by the link, out of the plurality of image data, are subject to be displayed in response to the operation input, the whole display and the digest display are each displayed with an image operating area which includes a parent image area, a child image area, and a selection frame, the selection frame indicating a parent image in the parent image area, the child image area including a plurality of child images linked to the parent image indicated by the selection frame, and an image indicated by the selection frame being highlighted in the whole display or the digest display, the selection frame surrounding image data corresponding to one parent image and image data corresponding to one child image linked to the one parent image, the image display controlling apparatus being operable to establish a link representing a parent-child relationship when an image in the child image area of the image operating area is placed over an image in the parent image area of the image operating area, and when an image in the parent image area of the image operating area is placed over another image in the parent image area of the image operating area, wherein when an image in the parent image area of the image operating area is placed over another image in the parent image area of the image operating area the image placed over becomes a child of the another image.