Abstract: This invention is to generate image data at a high speed in units of bands on the basis of input data while effectively utilizing limited resources. Each of compression/expansion circuits (201, 202) independently operates in a compression or expansion mode in accordance with a signal set in a register (205). When bitmap image data stored in a RAM (19) is to be simply compressed, a switch (206) is connected to a terminal (B) such that the compression/expansion circuits (201, 202) are substantially connected in parallel to efficiently perform compression. When compressed data must be edited, the compression/expansion circuit (201) is set in the expansion mode, and the compression/expansion circuit (202) is set in the compression mode. The switch (206) is connected to a terminal A such that the compression/expansion circuits (201, 202) are connected in series.

Abstract: The present invention provides a technique which can protect security of data until a regular user who transmits print data directs to start printing on the side of a printing apparatus even in an environment where a plurality of host computers on a network use a common printing apparatus, and which can print image data which has already been produced, as it is after the user gives instructions to start printing.