| 摘要 |
PURPOSE:To set a clipping area which is not limited by a rectangular area by calculating an area that is clipped for each update of raster via a function generating circuit in the processing where the data are transferred for each raster. CONSTITUTION:The boundary value of the Y coordinates of an area to be clipped is set to the clipping Y coordinate registers 7 and 8 and then to the function generating circuits 23 and 24 so as to successively generate the X coordinate value. Then the update of raster is controlled by a raster update control part 20, and the coordinate value to be drawn is generated and stored in a drawing X coordinate register 1 and a drawing Y coordinate register 2 respectively. At the same time, the X coordinate value corresponding to the raster to be processed is calculated via the function generating circuits 23 and 24 and stored in the clipping X coordinate register 5 and 6 respectively. A clipping deciding part 14 decides whether the drawing should be granted or inhibited to the XY coordinates which are decided by the contents of both registers 1 and 2. Thus the clipping operation is attained in an area defined by a curve. |
