colour palette

graphics, hardware (colour look-up table, CLUT) A device

which converts the logical colour numbers stored in each

pixel of video memory into physical colours, normally

represented as RGB triplets, that can be displayed on the

monitor. The palette is simply a block of fast RAM which

is addressed by the logical colour and whose output is split

into the red, green and blue levels which drive the actual

display (e.g. CRT).

The number of entries (logical colours) in the palette is the

total number of colours which can appear on screen

simultaneously. The width of each entry determines the number

of colours which the palette can be set to produce.

A common example would be a palette of 256 colours

(i.e. addressed by eight-bit pixel values) where each colour

can be chosen from a total of 16.7 million colours (i.e. eight

bits output for each of red, green and blue).

Changes to the palette affect the whole screen at once and can

be used to produce special effects which would be much slower

to produce by updating pixels.

(1997-06-03)