PURPOSE: To improve the efficiency of processing by adding header information regarding an image buffer to image data and inputting data to an unused buffer from the header information appropriately and previously when the image data is continuously printed.
CONSTITUTION: A multilevel image buffer 9 receives multilevel image data outputted from a scanner 5 as it is, while a binary image buffer 8 receives data that a binary/multilevel conversion circuit 12 binarizes. Viewing the image on a CRT 3, an operator distinguishes a binary area from a multilevel area, and stores information about the areas in an area control buffer 10. Then data in the buffers 8 and 9, area control buffer information and the header information are stored in an external storage device 17. The header information includes that the image is of both binary and multilevel, only binary or multilevel. When plural images are continuously printed, the header information shows the development of the image data prior to the unused buffer. Thus the efficiency of printing is improved.