| 摘要 |
PURPOSE:To perform Z sorting without providing a special memory by writing graphic data, to which a priority number is not given, in a memory after temporarily subjecting it to the concealment processing and giving the priority number to it on condition that all picture element data constituting the same data coincide with data in the memory. CONSTITUTION:Data read out from a frame memory 11 is temporarily stored in a register 12, and data of a segment to be described is temporarily stored in a register 13. Contents of both registers 12 and 13 are inputted to a calculator 14, and the operation of the calculator 14 is controlled by a control circuit 15. The calculator 14 calculates the difference between contents of registers 12 and 13 or outputs contents of registers 12 and 13 to the memory 11 as they are in accordance with the mode setting signal from the circuit 15. The calculator 14 supplies the discrimination signal, which indicates that contents of the register 12 are larger or contents of registers 12 and 13 are equal to each other, to the circuit 15, and the calculator 14 is controlled by the circuit 15. |
