Converts cubehelix HSL to RGB

colorspace_cubehelix.cpp

// Reference here: http://www.mrao.cam.ac.uk/~dag/CUBEHELIX/
skg_color128_t skg_col_helix128(float h, float s, float l, float alpha) {
	const float tau = 6.28318f;
	l = fminf(1,l);
	float angle = tau * (h+(1/3.f));
	float amp   = s * l * (1.f - l);

	float a_cos = cosf(angle);
	float a_sin = sinf(angle);
	float r = l + amp * (-0.14861f * a_cos + 1.78277f * a_sin);
	float g = l + amp * (-0.29227f * a_cos - 0.90649f * a_sin);
	float b = l + amp * ( 1.97294f * a_cos);
	r = fmax(0,fminf(1, r));
	g = fmax(0,fminf(1, g));
	b = fmax(0,fminf(1, b));
	return { r, g, b, alpha };
}