Precomputed 8-bit gamma correction lookup table.
Applies out = pow(in / 255, gamma) * 255 to a channel value. This compensates for a display's non-linear brightness response - on some cheap panels, near-black tones show a visible color tint because tiny per-channel differences (e.g. R=33 vs B=32) get amplified into a visible hue by the panel's own response curve, even though the exact same values render correctly at higher, well-saturated brightness.
There's no single correct gamma value for an unknown/undocumented panel - try values on both sides of 1.0 and compare on real hardware: gamma < 1.0 lifts (brightens) dark input values before they reach the panel; gamma > 1.0 compresses them further. 1.0 (the default) applies no correction.
