Gamma Correction

Gamma correction of images is used to optimize the usage of data type depth when encoding an image by taking advantage of the non-linear manner in which humans perceive light and color. This non-linearity must be compensated to achieve correct color reproduction. To do this, luminance of each of the linear red, green, and blue components is reduced to a non-linear form using an inverse transformation. This process is called gamma correction.

The oneIPL functions use the following basic equations to convert an RGB image to a gamma-corrected R’G’B’ image:

for R,G,B < 0.018

R' = 4.5R

G' = 4.5G

B' = 4.5B

for R,G,B≥ 0.018

R' = 1.099R0.45 - 0.099

G' = 1.099G0.45 - 0.099

B' = 1.099B0.45 - 0.099

Note

The channel intensity values are normalized to fit in the range [0..1]. The gamma value is equal to 1/0.45 = 2.22 in conformity with ITU Rec.709 specification (see [ITU709]).