cpu 32 determines the number of drawing processors necessary for execution of all the image processing within the required processing time included in the image processing command based on the calculated processing times and determines drawing processors in charge of the respective image processing step s 102 the details of the determination of the number of necessary drawing processors will be described later when the drawing processors necessary to realize the requirements of the image processing command have been determined the drawing control cpu 32 issues commands to the power source circuits among the power source circuits 51 to 53 provided for unnecessary drawing processors to stop power supply step s 103 by this operation power supply to the drawing processors other than the drawing processors necessary to realize the requirements of the image processing command is blocked then the drawing control cpu 32 performs initialization processing on the drawing processors determined to be used to realize the requirements of the image processing command to realize respective corresponding image processing functions step s 104 in the drawing processor initialized by the drawing control cpu 32 connection information to realize the designated image processing is read from the connection information storage part 43 and performed for the computing unit group 42 and the required image processing function is realized then in the respective drawing processors designated image processing is started with respect to input image data step s 105 then in the respective drawing processors when all the designated image processing has been performed the processing is terminated step s 106 next the details of the determination of the number of necessary drawing processors step s 102 shown in the flowchart of fig7 will be.