colour.CIECAM02_to_XYZ

colour.CIECAM02_to_XYZ(CIECAM02_specification, XYZ_w, L_A, Y_b, surround=CIECAM02_InductionFactors(F=1, c=0.69, N_c=1), discount_illuminant=False)[source]

Converts CIECAM02 specification to CIE XYZ tristimulus values.

This is the reverse implementation.

Parameters:
  • CIECAM02_specification (CIECAM02_Specification) – CIECAM02 colour appearance model specification. Correlate of Lightness \(J\), correlate of chroma \(C\) or correlate of colourfulness \(M\) and hue angle \(h\) in degrees must be specified, e.g. \(JCh\) or \(JMh\).
  • XYZ_w (array_like) – CIE XYZ tristimulus values of reference white.
  • L_A (numeric or array_like) – Adapting field luminance \(L_A\) in \(cd/m^2\), (often taken to be 20% of the luminance of a white object in the scene).
  • Y_b (numeric or array_like) – Relative luminance of background \(Y_b\) in \(cd/m^2\).
  • surround (CIECAM02_InductionFactors, optional) – Surround viewing conditions.
  • discount_illuminant (bool, optional) – Discount the illuminant.
Returns:

XYZ – CIE XYZ tristimulus values.
Return type:

ndarray
Raises:

ValueError – If neither C or M correlates have been defined in the CIECAM02_specification argument.

Warning

The output range of that definition is non standard!

Notes

  • CIECAM02_specification can also be passed as a compatible argument colour.utilities.as_namedtuple() definition.
  • Input CIE XYZ_w tristimulus values are in domain [0, 100].
  • Output CIE XYZ tristimulus values are in range [0, 100].

References

Examples

>>> specification = CIECAM02_Specification(J=41.731091132513917,
...                                        C=0.104707757171031,
...                                        h=219.048432658311780)
>>> XYZ_w = np.array([95.05, 100.00, 108.88])
>>> L_A = 318.31
>>> Y_b = 20.0
>>> CIECAM02_to_XYZ(specification, XYZ_w, L_A, Y_b)  
array([ 19.01...,  20...  ,  21.78...])