colour.RGB_to_ICtCp

colour.RGB_to_ICtCp(RGB, method='Dolby 2016', L_p=10000)[source]

Converts from ITU-R BT.2020 colourspace to \(IC_TC_P\) colour encoding.

Parameters
  • RGB (array_like) – ITU-R BT.2020 colourspace array.

  • method (str, optional) –

    {‘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’}, 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 / EOCF) 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 / OECF) 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 / EOCF) 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 / OECF) and a custom \(IC_TC_P\) matrix from [InternationalTUnion18]: ITU-R BT.2100-2 HLG method.

  • L_p (numeric, optional) – 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

\(IC_TC_P\) colour encoding array.

Return type

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. The effective domain of SMPTE ST 2084:2014 inverse electro-optical transfer function (EOTF / EOCF) is [0.0001, 10000].

Domain

Scale - Reference

Scale - 1

RGB

UN

UN

Range

Scale - Reference

Scale - 1

ICtCp

I : [0, 1]

CT : [-1, 1]

CP : [-1, 1]

I : [0, 1]

CT : [-1, 1]

CP : [-1, 1]

References

[Dolby16], [LPY+16]

Examples

>>> RGB = np.array([0.45620519, 0.03081071, 0.04091952])
>>> RGB_to_ICtCp(RGB)  
array([ 0.0735136...,  0.0047525...,  0.0935159...])
>>> RGB_to_ICtCp(RGB, method='ITU-R BT.2100-2 HLG')  
array([ 0.6256789..., -0.0198449...,  0.3591125...])