1. An image processing method, comprising the steps of: scanning respective pages of a document in an image processing apparatus; generating respective pieces of image data corresponding to the pages in a processor of said image processing apparatus; calculating, in said image processing apparatus, image density distributions in a primary scan direction and a secondary scan direction in each of the pages from the image data; determining, in said image processing apparatus, whether or not each of the pages contains isolated images that have different orientations according to the image density distributions; assigning, in said image processing apparatus, respective ones of the isolated images to new pages; identifying, in said image processing apparatus, respective orientations of the isolated images according to a result of character recognition for the image data; and setting respective orientations, in said image processing apparatus, of the isolated images in the new pages as respective upright orientations of the isolated images, calculating, in said image processing apparatus, respective summation values of image density for rows along the primary scan direction of the page, and obtaining the image density distribution in the secondary scan direction by arranging these summation values along the secondary scan direction; calculating, in said image processing apparatus, respective summation values of image density for columns along the secondary scan direction of the page, and obtaining the image density distribution in the primary scan direction by arranging these summation values along the primary scan direction; detecting, in said image processing apparatus, a blank area between the isolated images from the image density distributions of the primary scan direction and the secondary scan direction; and determining, in said image processing apparatus, that the page contains isolated images, if the blank area is detected.