curve correction

Gamma correction, or often simply gamma, is a nonlinear operation used to encode and decode luminance or tristimulus values in video or still image systems. Gamma correction is, in the simplest cases, defined by the following power-law expression:





V

out


=
A


V

in


γ





{\displaystyle V_{\text{out}}=A{V_{\text{in}}^{\gamma }}}
where the non-negative real input value




V

in




{\displaystyle V_{\text{in}}}
is raised to the power



γ


{\displaystyle \gamma }
and multiplied by the constant A, to get the output value




V

out




{\displaystyle V_{\text{out}}}
. In the common case of A = 1, inputs and outputs are typically in the range 0–1.
A gamma value



γ
<
1


{\displaystyle \gamma <1}
is sometimes called an encoding gamma, and the process of encoding with this compressive power-law nonlinearity is called gamma compression; conversely a gamma value



γ
>
1


{\displaystyle \gamma >1}
is called a decoding gamma and the application of the expansive power-law nonlinearity is called gamma expansion.

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