colour.CIECAM02_to_XYZ

colour.CIECAM02_to_XYZ(specification: colour.appearance.ciecam02.CAM_Specification_CIECAM02, XYZ_w: ArrayLike, L_A: FloatingOrArrayLike, Y_b: FloatingOrArrayLike, surround: colour.appearance.ciecam02.InductionFactors_CIECAM02 = VIEWING_CONDITIONS_CIECAM02['Average'], discount_illuminant: bool = False) → numpy.ndarray[source]

Convert from CIECAM02 specification to CIE XYZ tristimulus values.

Parameters

  • specification (colour.appearance.ciecam02.CAM_Specification_CIECAM02) – 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 (ArrayLike) – CIE XYZ tristimulus values of reference white.

  • L_A (FloatingOrArrayLike) – 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 (FloatingOrArrayLike) – Luminous factor of background \(Y_b\) such as \(Y_b = 100 x L_b / L_w\) where \(L_w\) is the luminance of the light source and \(L_b\) is the luminance of the background. For viewing images, \(Y_b\) can be the average \(Y\) value for the pixels in the entire image, or frequently, a \(Y\) value of 20, approximate an \(L^*\) of 50 is used.

  • surround (colour.appearance.ciecam02.InductionFactors_CIECAM02) – Surround viewing conditions.

  • discount_illuminant (bool) – Discount the illuminant.

Returns

CIE XYZ tristimulus values.

Return type

numpy.ndarray

Raises

ValueError – If neither C or M correlates have been defined in the CAM_Specification_CIECAM02 argument.

Notes

Domain

Scale - Reference

Scale - 1

CAM_Specification_CIECAM02.J

[0, 100]

[0, 1]

CAM_Specification_CIECAM02.C

[0, 100]

[0, 1]

CAM_Specification_CIECAM02.h

[0, 360]

[0, 1]

CAM_Specification_CIECAM02.s

[0, 100]

[0, 1]

CAM_Specification_CIECAM02.Q

[0, 100]

[0, 1]

CAM_Specification_CIECAM02.M

[0, 100]

[0, 1]

CAM_Specification_CIECAM02.H

[0, 360]

[0, 1]

XYZ_w

[0, 100]

[0, 1]

Range

Scale - Reference

Scale - 1

XYZ

[0, 100]

[0, 1]

References

[Fai04], [LL13], [MFH+02], [Wikipedia07b]

Examples

>>> specification = CAM_Specification_CIECAM02(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...])

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