colour.models.hdr_cie_lab Module¶
hdr-CIELAB Colourspace¶
Defines the hdr-CIELAB colourspace transformations:
References
[1] | Fairchild, M. D., & Wyble, D. R. (2010). hdr-CIELAB and hdr-IPT: Simple Models for Describing the Color of High-Dynamic-Range and Wide-Color-Gamut Images. In Proc. of Color and Imaging Conference (pp. 322–326). ISBN:9781629932156 |
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colour.models.hdr_cie_lab.
XYZ_to_hdr_CIELab
(XYZ, illuminant=array([ 0.3457, 0.3585]), Y_s=0.2, Y_abs=100)[source]¶ Converts from CIE XYZ tristimulus values to hdr-CIELAB colourspace.
Parameters: - XYZ (array_like) – CIE XYZ tristimulus values.
- illuminant (array_like, optional) – Reference illuminant xy chromaticity coordinates or CIE xyY colourspace array.
- Y_s (numeric or array_like) – Relative luminance \(Y_s\) of the surround in domain [0, 1].
- Y_abs (numeric or array_like) – Absolute luminance \(Y_{abs}\) of the scene diffuse white in \(cd/m^2\).
Returns: hdr-CIELAB colourspace array.
Return type: ndarray
Notes
- Conversion to polar coordinates to compute the chroma \(C_{hdr}\)
and hue \(h_{hdr}\) correlates can be safely performed with
colour.Lab_to_LCHab()
definition. - Conversion to cartesian coordinates from the Lightness
\(L_{hdr}\), chroma \(C_{hdr}\) and hue \(h_{hdr}\)
correlates can be safely performed with
colour.LCHab_to_Lab()
definition. - Input CIE XYZ tristimulus values are in domain [0, math:infty].
- Input illuminant xy chromaticity coordinates or CIE xyY colourspace array are in domain [0, \(\infty\)].
Examples
>>> XYZ = np.array([0.07049534, 0.10080000, 0.09558313]) >>> XYZ_to_hdr_CIELab(XYZ) array([ 24.9020664..., -46.8312760..., -10.14274843])
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colour.models.hdr_cie_lab.
hdr_CIELab_to_XYZ
(Lab_hdr, illuminant=array([ 0.3457, 0.3585]), Y_s=0.2, Y_abs=100)[source]¶ Converts from hdr-CIELAB colourspace to CIE XYZ tristimulus values.
Parameters: - Lab_hdr (array_like) – hdr-CIELAB colourspace array.
- illuminant (array_like, optional) – Reference illuminant xy chromaticity coordinates or CIE xyY colourspace array.
- Y_s (numeric or array_like) – Relative luminance \(Y_s\) of the surround in domain [0, 1].
- Y_abs (numeric or array_like) – Absolute luminance \(Y_{abs}\) of the scene diffuse white in \(cd/m^2\).
Returns: CIE XYZ tristimulus values.
Return type: ndarray
Notes
- Input illuminant xy chromaticity coordinates or CIE xyY colourspace array are in domain [0, \(\infty\)].
- Output CIE XYZ tristimulus values are in range [0, math:infty].
Examples
>>> Lab_hdr = np.array([24.90206646, -46.83127607, -10.14274843]) >>> hdr_CIELab_to_XYZ(Lab_hdr) array([ 0.0704953..., 0.1008 , 0.0955831...])
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colour.models.hdr_cie_lab.
exponent_hdr_CIELab
(Y_s, Y_abs)[source]¶ Computes hdr-CIELAB colourspace Lightness \(\epsilon\) exponent.
Parameters: - Y_s (numeric or array_like) – Relative luminance \(Y_s\) of the surround in range [0, 1].
- Y_abs (numeric or array_like) – Absolute luminance \(Y_{abs}\) of the scene diffuse white in \(cd/m^2\).
Returns: hdr-CIELAB colourspace Lightness \(\epsilon\) exponent.
Return type: array_like
Examples
>>> exponent_hdr_CIELab(0.2, 100) 1.8360198...