colour.ICtCp_to_XYZ#

colour.ICtCp_to_XYZ(ICtCp: ArrayLike, illuminant=CCS_ILLUMINANTS['CIE 1931 2 Degree Standard Observer']['D65'], chromatic_adaptation_transform: Literal['Bianco 2010', 'Bianco PC 2010', 'Bradford', 'CAT02 Brill 2008', 'CAT02', 'CAT16', 'CMCCAT2000', 'CMCCAT97', 'Fairchild', 'Sharp', 'Von Kries', 'XYZ Scaling'] | str | None = 'CAT02', method: Literal['Dolby 2016', 'ITU-R BT.2100-1 HLG', 'ITU-R BT.2100-1 PQ', 'ITU-R BT.2100-2 HLG', 'ITU-R BT.2100-2 PQ'] | str = 'Dolby 2016', L_p: float = 10000) → NDArrayFloat[source]#

Convert from \(IC_TC_P\) colour encoding to CIE XYZ tristimulus values.

Parameters:

ICtCp (ArrayLike) – \(IC_TC_P\) colour encoding array.
illuminant – Source illuminant chromaticity coordinates.
chromatic_adaptation_transform (Literal['Bianco 2010', 'Bianco PC 2010', 'Bradford', 'CAT02 Brill 2008', 'CAT02', 'CAT16', 'CMCCAT2000', 'CMCCAT97', 'Fairchild', 'Sharp', 'Von Kries', 'XYZ Scaling'] | str | None) – Chromatic adaptation transform.
method (Literal['Dolby 2016', 'ITU-R BT.2100-1 HLG', 'ITU-R BT.2100-1 PQ', 'ITU-R BT.2100-2 HLG', 'ITU-R BT.2100-2 PQ'] | str) –
Computation method. Recommendation ITU-R BT.2100 defines multiple variants of the \(IC_TC_P\) colour encoding:
- ITU-R BT.2100-1
  - SMPTE ST 2084:2014 inverse electro-optical transfer function (EOTF) and the \(IC_TC_P\) matrix from [Dolby16]: Dolby 2016, ITU-R BT.2100-1 PQ, ITU-R BT.2100-2 PQ methods.
  - Recommendation ITU-R BT.2100 Reference HLG opto-electrical transfer function (OETF) and the \(IC_TC_P\) matrix from [Dolby16]: ITU-R BT.2100-1 HLG method.
- ITU-R BT.2100-2
  - SMPTE ST 2084:2014 inverse electro-optical transfer function (EOTF) and the \(IC_TC_P\) matrix from [Dolby16]: Dolby 2016, ITU-R BT.2100-1 PQ, ITU-R BT.2100-2 PQ methods.
  - Recommendation ITU-R BT.2100 Reference HLG opto-electrical transfer function (OETF) and a custom \(IC_TC_P\) matrix from [InternationalTUnion18]: ITU-R BT.2100-2 HLG method.
L_p (float) – Display peak luminance \(cd/m^2\) for SMPTE ST 2084:2014 non-linear encoding. This parameter should stay at its default \(10000 cd/m^2\) value for practical applications. It is exposed so that the definition can be used as a fitting function.

Returns:

CIE XYZ tristimulus values.

Return type:

numpy.ndarray

Warning

The underlying SMPTE ST 2084:2014 transfer function is an absolute transfer function.

Notes

The ITU-R BT.2100-1 PQ and ITU-R BT.2100-2 PQ methods are aliases for the Dolby 2016 method.
The underlying SMPTE ST 2084:2014 transfer function is an absolute transfer function, thus the domain and range values for the Reference and 1 scales are only indicative that the data is not affected by scale transformations.

Domain	Scale - Reference	Scale - 1
`ICtCp`	`I` : [0, 1] `CT` : [-1, 1] `CP` : [-1, 1]	`I` : [0, 1] `CT` : [-1, 1] `CP` : [-1, 1]

Domain

Scale - Reference

Scale - 1

ICtCp

I : [0, 1]

CT : [-1, 1]

CP : [-1, 1]

I : [0, 1]

CT : [-1, 1]

CP : [-1, 1]

Range	Scale - Reference	Scale - 1
`XYZ`	`UN`	`UN`

References

[Dolby16], [LPY+16]

Examples

>>> ICtCp = np.array([0.06858097, -0.00283842, 0.06020983])
>>> ICtCp_to_XYZ(ICtCp)  
array([ 0.2065400...,  0.1219722...,  0.0513695...])
>>> ICtCp = np.array([0.59242792, -0.03740730, 0.25122675])
>>> ICtCp_to_XYZ(ICtCp, method="ITU-R BT.2100-2 HLG")  
array([ 0.2065400...,  0.1219722...,  0.0513695...])