| 摘要 |
PURPOSE:To reduce the volume of hardware and to improve operability by permitting a shared register to specify transparency when a specific color is set transparent and when the color of the corresponding picture element of a back picture element plane is displayed. CONSTITUTION:A transparency specification register 30 specifies (sets A and B to '1' in 16-notation, for instance) a color to be transparent through all picture element planes. With respect to the picture element planes 11-1n, information of coloring corresponding picture elements is synchronizingly fetched to registers 21-2n. At that time, multiplexers 61-6n compare the values of the registers 21-2n with that of a register 31 in regard to coincidence of value, and informs decision parts 41-4n of the comparison information. Since information on a preplane is inputted to the decision parts 41-4n, the multiplexers decide taking into consideration of said information. As the decided output is inputted to an OR circuit 53, the picture elements comprising the preplane are colored and displayed unless the register 30 specifies transparency. If the register does, the colors of a postplane are sequentially displayed.
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