Overview - 1.1 English

PG285 Gamma Look Up Table

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1.1 English

Gamma correction, also known as gamma compression or encoding, is used to encode linear luminance or RGB values to match the non-linear characteristics of display devices. Gamma correction helps to map data into a more perceptually uniform domain, so as to optimize perceptual performance of a limited signal range, such as a limited number of bits in each RGB component.

Gamma correction is, in the simplest cases, defined by This Equation

Equation 1-1


where the input and output values are between 0 and 1 ( This Figure ). The case γ <1 is often called gamma compression and γ >1 is called gamma expansion.

When used in conjunction with an embedded or external processor, the Gamma LUT core supports frame-by-frame dynamic reprogramming of the gamma tables. The gamma tables can be reprogrammed with arbitrary functions, supporting a wide range of applications, such as intensity correction, feature enhancement, lin-log, log-lin conversion, and thresholding.

Figure 1-1: Gamma Correction

X-Ref Target - Figure 1-1


The Gamma LUT core is implemented as a set of LUTs that are used to perform the data transformation. The width of the data determines the number of entries in the LUT. For example, 8-bit data would require 2 8 (256) entries in the LUT. The width of the data also determines the width of each entry in the LUT. For example, 10-bit data would require that each entry in the table be 10-bit wide.