When a plurality of image data are to be compressed, an image correlation information
extraction unit extracts respective image correlation information of image data,
using first image data as reference image data. An encoding unit compresses the
extracted image correlation information to produce encoded data. A data output
unit outputs the compressed data and the reference image data to a page memory.
When the compressed data are to be restored, a data input unit supplies the image
correlation data input from the page memory to an image correlation information
decoding unit, and supplies the reference image data to an image restoring unit.
The image correlation information decoding unit decodes the image correlation data
into the respective image correlation information and supplies the image correlation
information to the image restoring unit. The image restoring unit restores the
plural image data from the respective image correlation information and the reference
image data.
