| 摘要 |
<p>APPARATUS FOR CONTROLLING THE COLORS DISPLAYED BY A RASTER GRAPHIC SYSTEM Apparatus for controlling the colors displayed by a raster graphic system, which includes a color cathode ray tube. The tube is provided with an orthogonal array of picture elements (PIXELS), with each PIXEL having a unique binary address. An addressable memory is provided with memory locations, the addresses of which correspond to those of one of a set of PIXELS. The information stored at each addressable location includes a set of background/foreground control bits and a group of behavior bits. The background/foreground control bits are read out of a memory during a memory cycle and stored in a shift register. At the same time, the behavior bits are read out of the memory and are applied to an escape-code detector and to a foreground behavior register and a background behavior register, each of which is capable of storing a group of behavior bits. The shift register shifts out one background/foreground control bit for each PIXEL clock pulse which determines the set of behavior bits stored in the background and foreground registers to be used in forming a color index. The color index, which includes a group of behavior bits and the background/foreground control bit, is then used as an address to a color look-up memory, and at which each addressable location are stored typically eight bits which determine the color. Color control signals read out of the color look-up memory are applied to D/A converters to produce analog signals to control the intensity of the red, green and blue guns of a cathode ray tube. One set of the behavior bits is defined as constituting an escape code. Whenever this particular set of behavior bits is read out of the behavior memory, that set is not stored in either the background or foreground behavior registers. When the escape code is detected, the next set of behavior bits read out of the behavior memory is stored into the background behavior register. In the absence of an escape code being detected, the behavior bits are stored in the foreground behavior register. The bits in the background behavior register remain the same until the next escape code is detected, at which time the next set of behavior bits is stored into the background behavior register.</p> |
