Color & Graphics

//! requires hueToRgb
fn hslToRgb(hsl: vec3<f32>) -> vec3<f32> {
  let h = hsl.x;
  let s = hsl.y;
  let l = hsl.z;
  
  if (s == 0.0) {
    return vec3(l); // achromatic
  }
  
  let q = select(l * (1.0 + s), l + s - l * s, l < 0.5);
  let p = 2.0 * l - q;
  
  return vec3(
    hueToRgb(p, q, h + 1.0 / 3.0),
    hueToRgb(p, q, h),
    hueToRgb(p, q, h - 1.0 / 3.0)
  );
}

fn hueToRgb(p: f32, q: f32, t: f32) -> f32 {
  var t_adj = t;
  if (t_adj < 0.0) { t_adj += 1.0; }
  if (t_adj > 1.0) { t_adj -= 1.0; }
  if (t_adj < 1.0 / 6.0) { return p + (q - p) * 6.0 * t_adj; }
  if (t_adj < 1.0 / 2.0) { return q; }
  if (t_adj < 2.0 / 3.0) { return p + (q - p) * (2.0 / 3.0 - t_adj) * 6.0; }
  return p;
}

fn linearToSrgb(color: vec3<f32>) -> vec3<f32> {
  return pow(color, vec3(1.0 / 2.2));
}

fn palette(t: f32, a: vec3<f32>, b: vec3<f32>, c: vec3<f32>, d: vec3<f32>) -> vec3<f32> {
  return a + b * cos(6.28318 * (c * t + d));
}

fn srgbToLinear(color: vec3<f32>) -> vec3<f32> {
  return pow(color, vec3(2.2));
}