srgb_to_linear_fast

The fast path uses a piecewise linear interpolant of the exact transfer curve. Sampling in encoded space concentrates linear-domain samples near black. A faster srgb_to_linear for values in [0, 1]: linear interpolation over a 64-segment table of the exact curve, built at compile time, so there is no pow call at run time. The error is below about 0.002 in the linear result. Inputs of 1 or more fall back to the exact curve, and the linear segment below 0.04045 is exact.

#import "Math";
x := srgb_to_linear_fast(0.5);
assert(abs(x - srgb_to_linear(0.5)) < 0.002);

srgb_to_linear_fast :: (x: float) -> float

#import "Math";
x := srgb_to_linear_fast(0.5);
assert(abs(x - srgb_to_linear(0.5)) < 0.002);

srgb_to_linear_fast :: (c: Vector3) -> Vector3

srgb_to_linear_fast :: (c: Vector4) -> Vector4