class colour.RLAB_Specification[source]

Defines the RLAB colour appearance model specification.

This specification has field names consistent with the remaining colour appearance models in colour.appearance but diverge from Fairchild (2013) reference.

  • J (numeric or array_like) – Correlate of Lightness \(L^R\).
  • C (numeric or array_like) – Correlate of achromatic chroma \(C^R\).
  • h (numeric or array_like) – Hue angle \(h^R\) in degrees.
  • s (numeric or array_like) – Correlate of saturation \(s^R\).
  • HC (numeric or array_like) – Hue \(h\) composition \(H^C\).
  • a (numeric or array_like) – Red-green chromatic response \(a^R\).
  • b (numeric or array_like) – Yellow-blue chromatic response \(b^R\).


  • This specification is the one used in the current model implementation.


[Fai96], [Fai13h]

Create new instance of RLAB_Specification(J, C, h, s, HC, a, b)


Initialize self. See help(type(self)) for accurate signature.


count Return number of occurrences of value.
index Return first index of value.


C Alias for field number 1
HC Alias for field number 4
J Alias for field number 0
a Alias for field number 5
b Alias for field number 6
h Alias for field number 2
s Alias for field number 3