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Gamma Correction

Given a desired intensity I and the Red-Green-Blue components of the basic color (R, G, B), the color at full intensity, the RGB components (r, g, b) that define the screen or hardcopy color are given by 1 of 3 mappings, known as gamma corrections. For x = each of r, g, and b, and similarly for X,

x = (1 / 0.5198) (1 / 10^{[2.3 - (2.3 - 0.28)IX]} - 0.00501187)
   = 0.00964192 ( 10^2.02IX - 1 )

is the default or "CGS" mapping,

x = IX

in the no gamma correction mode, and

x = 1 = 0.00964192 [ 10^{2.02(1 - IX)} - 1 ]

in reverse-CGS mode. These mappings may be specified by QPALET GAMMA, followed by CGS, NONE, or REVERSE. This setting will not take effect until another command forces the color map to be recomputed. Since R = G = B = 0 for black, the intensity variations are reversed, and I is replaced by (1 - I) in the above formulae.