1. An image displaying sheet, comprising: a composite image comprising plural composite image units, wherein said plural composite image units are arranged in a two-dimensional array, wherein said plural composite image units have a first image period along a first direction and a second image period along a second direction, wherein said first direction and said second direction are different; and a lens array stacked on said composite image, wherein said lens array has a first surface and a second surface opposite to said first surface, wherein plural lenticular lenses are distributed on said first surface, and said composite image is stacked on said second surface, wherein said plural lenticular lenses on said first surface have a first lens period along said first direction and a second lens period along said second direction; wherein said composite image is produced by steps of: providing J groups of original images corresponding to images of an object from plural viewpoints, where J is a positive integer larger than 1, wherein each group consists of N original images and each group forms an intermediate image, where N is a positive integer larger than 1; sorting said N original images so that each of said N original images is assigned as an M-th original image, wherein M sequentially denotes plural positive integers from 1 to N; slicing each M-th original image into plural columns of M-th sub-image strips along a direction parallel with said second direction; sequentially selecting (M+N×C)-th columns of M-th sub-image strips of each M-th original image with M proceeding from 1 through N, and C proceeding from 0 through a preset number equal to or larger than 1; combining said sequentially selected (M+N×C)-th columns of M-th sub-image strips of said M-th original image to form an intermediate image; repeating said sorting, slicing, selecting and combining steps for the other group of groups of original images, thereby forming J intermediate images; sorting said J intermediate images, so that each of said J intermediate images is assigned as a K-th intermediate image, wherein K sequentially denotes plural positive integers from 1 to J; slicing each K-th intermediate image into plural rows of K-th intermediate sub-image strips of said K-th intermediate image along a direction parallel with said first direction; sequentially selecting (K+J×L)-th rows of K-th intermediate sub-image strips of said K-th intermediate image with K proceeding from 1 through J, and L proceeding from 0 through a preset number equal to or larger than 1; and combining said sequentially selected (K+J×L)-th rows of K-th intermediate sub-image strips of said K-th intermediate image to form said composite image.