An apparatus generates display data on a display unit. An image constructing unit constructs an image of an image list including a plurality of images each corresponding to an image data file. A data output unit outputs first display data of the image list, and then, when a switching command is received from a user, outputs second display data of the image list in response to the switching command. A confirmation calculating unit calculates a degree of confirmation indicating whether a user confirmation is performed for each of the images in the image list. An image modifying unit modifies the images in the image list based on the degree of confirmation.