Each data of R, G, and B stored in the multi-purpose memory 55 is expressed as 22 ???i+2???k+l using integers i, k, and l where i is intensity information which takes the value as follows: 0???i???22 and k is 0 or 1, which represents information such as label information, and l is 0 or 1 which is the information showing whether or not line drawings are carried out.