PURPOSE: To apply an edge film algorithm to a non-zero winding rule, as well by operating arithmetically a point in the inside of a specific trapezoid in accordance with the result of decision of a direction vector of each side, and writing it in an image memory.

CONSTITUTION: An image memory 5 is constituted of an (n)-bit/pixel (n denotes a natural number), and image data are stored by a bit image as the multivalue data of (n) bits against one pixel. Also, an in-trapezoid coordinate generating means 2 defines a straight line being parallel to the Y direction coordinate axis in the vicinity of a polygon for executing painting-out, and generates the coordinate of a point in the inside of a trapezoid obtained by drawing horizontal line to this straight line. In the case a direction vector deciding means 3 decides that the Y direction vector of the side polygon is positive, an arithmetic operation wiring means adds '1' to the data of the image memory 5 to the point in the inside of the trapezoid generated, based on its side, and '1' is subtracted in the case of negative. Subsequently, only in an area except '0', the plotting processing of a painting-out pattern is executed.