When a user inputs an image addition instruction from a UI input unit, a job registration unit registers a job corresponding to the instruction in a job list for each type of processing. When undo is input from the UI input unit, a current position pointer prepared for each type of processing returns to the immediately preceding job. When redo is input, the current position pointer moves to the immediately succeeding job. When a processing execution instruction is input, out of jobs registered in the job list, the job indicated by the current position pointer and preceding jobs are executed in a predetermined order.