| 摘要 |
PURPOSE:To print only in an extracted arbitrary area by comparing a clipping area data written in a clipping buffer with print data, and writing a prescribed value in a frame buffer based on the result of said comparison. CONSTITUTION:A poligon shape formed by connecting coordinate values C0-C3 is a clipping area C, and only the straight line included in said polygon is to be printed. The coordinate values C0-C3 are transmitted to a clipping area paint-out circuit 15, '1' is written in the clipping buffer 16 and at the same time transmitted to an in-area paint-out circuit 15-2 in order to write '1' in the whole area C. A line segment P0, P1 which is print data, too, undergoes a window clipping and is transmitted to a straight line generator 17, and an address calculation part 15-1 calculate the addresses. The data is written in the frame buffer 19 via an AND circuit 18-1 corresponding to the result of the comparison, so that only the area written in the buffer 16 is made writable in a buffer 19, hence only the line segment P2, P3 is written in the buffer 19.
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