A storage area where compressed data is stored is divided into a plurality of divided areas having a data length of Ls. Each divided area is divided into two areas, a first area having a data length of Ld and a second area having a data length of La. A plurality of first areas are gathered starting from the upper address to the lower address, whereby a memory area for compressed image data is composed. A plurality of second areas are gathered starting from the upper address to the lower address, whereby a memory area for compressed attribute data is composed. Compressed image data is sequentially written starting from the upper address to the lower address of the memory area for compressed image data. Compressed attribute data is sequentially written starting from the upper address to the lower address of the memory area for compressed attribute data.