| 摘要 |
PURPOSE:To plot a clipped graphic with simple logic by plotting the graphic in a first memory and afterwards, transferring an area overlapped with a clip frame to a second memory with OR logic. CONSTITUTION:According to plotted information, a plotting processing part 3 plots a straight line AB, for example. In such a case, plotting from a starting point A to an ending point B of the straight line is executed in a work memory 1 by using DDA logic, for example, regardless of whether the straight line AB and a clip flame C are crossed or not. Next, out of the straight line AB plotted in the work memory 1, a part in the clip frame C, namely, a straight line AD is transferred to a memory 2 for display by a transfer processing part 4. At such a time, the transfer is executed by using the OR logic so that the straight line already plotted in the memory 2 for display can not be erased, and a display part 5 displays the straight line AD plotted in the memory 2 for display. Thus, it is not necessary to calculate an intersection point between the graphic AB and the clip frame C, and without using the complicated logic, the graphic can be plotted in the clip frame. |
