1. An image processing apparatus, comprising: an image acquiring section configured to acquire one or more images; an image analysis information acquiring section configured to acquire image analysis information on each of the one or more images; a theme information storage section configured to store information on photography tendencies of images in association with each of one or more themes; a theme determining section configured to determine a main theme representing a theme of each group of images related to each other among the one or more images and a subtheme representing a theme of each of the one or more images based on the information on photography tendencies of images associated with each of the one or more themes and the image analysis information on each of the one or more images; and a theme information output section configured to output information on the main theme and information on the subtheme.