gistfile1.glsl

vec4 ApplyColorGrading(vec4 color, in sampler2D ramp)
{
	// 3d texture unwrapped to 256x16
	vec2 offset = vec2(0.5f / 256.0f, 0.5f / 16.0f);
	float scale = 15.0f / 16.0f; 

	// even and fractional parts of blue component
	float blueInt = floor(color.b * 15.0) / 16.0f;
	float blueFract = color.b * 15.0f - blueInt * 16.0f;

	// UV
	vec2 uv = vec2(
		blueInt + color.r * scale / 16.0f,
		color.g * scale
	);

	// uv offsets
	vec2 duv0 = vec2(0, 0);
	vec2 duv1 = vec2(1.0 / 16.0, 0.0);

	// LUT samples
	vec4 lut0 = texture(ramp, offset + uv + duv0);
	vec4 lut1 = texture(ramp, offset + uv + duv1);

	return mix(lut0, lut1, blueFract);
}