1. A still image compressing apparatus comprising: a memory to store image data; a sub-image generator to generate a plurality of same-resolution sub-images from a still image; and a moving image compressor to form a moving image having the sub-images as frames of the moving image, and compress the moving image to form a compressed representation of the still image; wherein the moving image is generated to store the still image when a storage capacity of the memory is not sufficient to store additional data.