Abstract: A color graphics system for use with a computer. The color graphics system utilizes a look-up table having index values to be stored in a frame buffer. The look-up table is addressed by providing color information, such as RGB color information to the table. The index values may be used to index a second look-up table for providing color information, such as RGB color information. The present invention further disclosed methods of insuring index values provided by the look-up table closely approximate the desired color within the available color space. Further the present invention provided methods for performing arithmetic transfer operations on colors represented by indexes in the frame buffer.

Abstract: A method for building an inverse color look-up table in a color graphics system. The inverse color look-up table accepts as an address input RGB color information and provides as a data output index information for indexing a color look-up table. The method initializes an array of data elements, each of said data elements for storing said index information, each of said data elements corresponding to a color position in RGB color space. A first index value is stored in the array, the first index value corresponding to an index for the color look-up table. The first index value is stored in a first of the data elements, the first data element corresponding to a color represented by the first index value in the color look-up table. An address of the first data element is also stored in a queue means. For a second of the data elements, it is determined whether the second data element has been assigned an index value.