| 摘要 |
A color video display apparatus displays a first image represented by luminance and color difference data stored in a VRAM and a second image represented by color codes stored in the same VRAM on a screen of a CRT display unit in a superimposed relation. Each address of the VRAM stores the luminance data and an attribute bit of the corresponding display dot of the first image, and the color difference data is formed with respect to each group of a predetermined number of display dots of the first image and stored in a predetermined number of addresses of the VRAM. The color code of each dot of the second image is stored in the corresponding addresses of the VRAM. The data sequentially read from the addresses of the VRAM are shifted into a register group composed of a predetermined number of registers. Data contained in specific bits of the registers is transferred to another register each time the predetermined number of data are read from the VRAM, and is outputted from the another register as the color difference data. When the attribute bit contained in specific one of the registers of the register group is "0", color data representative of a color of the corresponding display dot is formed from the luminance data contained in the specific register and the color difference data contained in the another register. On the other hand, when the attribute bit contained in the specific register is "1", the color data is formed by a look-up table from the color code contained in the specific register.
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