class Term::ANSIColor::RGBColorMetrics::CIELab::CIELabTriple

def self.from_rgb_triple(rgb_triple)
  r, g, b = normalize_rgb_triple rgb_triple
  x =  0.436052025 * r + 0.385081593 * g + 0.143087414 * b
  y =  0.222491598 * r + 0.71688606  * g + 0.060621486 * b
  z =  0.013929122 * r + 0.097097002 * g + 0.71418547  * b
  xr = x / 0.964221
  yr = y
  zr = z / 0.825211
  eps = 216.0 / 24389
  k = 24389.0 / 27
  fx = xr > eps ? xr ** (1.0 / 3) : (k * xr + 16) / 116
  fy = yr > eps ? yr ** (1.0 / 3) : (k * yr + 16) / 116
  fz = zr > eps ? zr ** (1.0 / 3) : (k * zr + 16) / 116
  l = 2.55 * ((116 * fy) - 16)
  a = 500 * (fx - fy)
  b = 200 * (fy - fz)
  new(l.round, a.round, b.round)
end