Sets the gamma lookup tables for the display for each color component. Each table is an array of 256 Uint8 values. The display values for each color component will be translated via the lookup table before being displayed (if supported). Gamma tables consisting of the sequence of numbers from 0..255 would be an identity table (i.e., 1:1 with no adjustment being made).
This function adjusts the gamma based on lookup tables, you can also have the gamma calculated based on a "gamma function" parameter with SDL_SetGamma.
Not all display hardware is able to change gamma.