Graphic card with two color look up tables

Abstract

The present invention provides a display subsystem which includes a frame buffer, a Digital to Analog Converter (DAC), a first color look up table and a second color look up table. The first color look up table is located in front of the frame buffer. The second color look up table is located between the frame buffer and the DAC. When the display subsystem receives a command that involves pixels from a Device Independent Bit Map (DIB) file, the translation table provided with the DIB is stored in the first color look up table. This translation table has a number of entries equal to the number of combinations available with the particular DIB format. For example, if the DIB has a one bit color format the first translation table has two entries one for each possible state of the color bits in the DIB. If the DIB uses a four bit color format the first table has sixteen entries, if the DIB uses an eight bit color format the table would have two hundred and fifty six entries, etc. The length of each entry in the first translation table conforms to the number of color bit planes in frame buffer. For example if the frame buffer accommodates twenty four bits for a true color display, each entry in the first translation table would have twenty four bits. The second color translation table is used to operate on the color bits which are read from the frame buffer. The second translation table translates the logical color information in the frame buffer into bits which generate the desired colors on the display.