The invention is directed to a technique for realtime processing of photographed pictures with less memory requirements. An image compressor compresses unit images, and so on of a given source picture individually. By converting reference data of compressed unit images and so on, the image compressor creates compressed data of the source picture. From the image compressor, a reference parameter generator receives original reference data corresponding to each unit image and so on having undergone the reference data conversion. An image decompressor retrieves a plurality of compressed unit images, and so on in an order suitable for a specified image editing operation. The image processor outputs the decompressed unit images after editing them to effect the specified image editing operation.