colour.models.hunter_lab Module¶

Hunter L,a,b Colour Scale¶

Defines the Hunter L,a,b colour scale transformations:

XYZ_to_K_ab_HunterLab1966()
XYZ_to_Hunter_Lab()
Hunter_Lab_to_XYZ()

References

[1]	HunterLab. (2008). Hunter L,a,b Color Scale. Retrieved from http://www.hunterlab.se/wp-content/uploads/2012/11/Hunter-L-a-b.pdf

colour.models.hunter_lab.XYZ_to_K_ab_HunterLab1966(XYZ)[source]¶

Converts from whitepoint CIE XYZ tristimulus values to Hunter L,a,b \(K_{a}\) and \(K_{b}\) chromaticity coefficients.

Parameters:	XYZ (array_like) – Whitepoint CIE XYZ tristimulus values.
Returns:	Hunter L,a,b \(K_{a}\) and \(K_{b}\) chromaticity coefficients.
Return type:	ndarray

Notes

Input CIE XYZ tristimulus values are in domain [0, 100].

References

[2]	HunterLab. (2008). Illuminant Factors in Universal Software and EasyMatch Coatings. Retrieved from https://support.hunterlab.com/hc/en-us/article_attachments/201437785/an02_02.pdf

Examples

>>> XYZ = np.array([109.850, 100.000, 35.585])
>>> XYZ_to_K_ab_HunterLab1966(XYZ)  
array([ 185.2378721...,   38.4219142...])

colour.models.hunter_lab.XYZ_to_Hunter_Lab(XYZ, XYZ_n=array([ 96.38, 100., 82.45]), K_ab=array([ 173.51, 58.48]))[source]¶

Converts from CIE XYZ tristimulus values to Hunter L,a,b colour scale.

Parameters:	XYZ (array_like) – CIE XYZ tristimulus values. XYZ_n (array_like, optional) – Reference illuminant tristimulus values. K_ab (array_like, optional) – Reference illuminant chromaticity coefficients, if K_ab is set to None it will be computed using `XYZ_to_K_ab_HunterLab1966()`.
Returns:	Hunter L,a,b colour scale array.
Return type:	ndarray

Notes

Input CIE XYZ and reference illuminant tristimulus values are in domain [0, 100].
Output Lightness \(L^*\) is in range [0, 100].

Examples

>>> XYZ = np.array([0.07049534, 0.10080000, 0.09558313]) * 100
>>> D50 = HUNTERLAB_ILLUMINANTS[
...     'CIE 1931 2 Degree Standard Observer']['D50']
>>> XYZ_to_Hunter_Lab(XYZ, D50.XYZ_n, D50.K_ab)   
array([ 31.7490157..., -15.1146262...,  -2.7866075...])

colour.models.hunter_lab.Hunter_Lab_to_XYZ(Lab, XYZ_n=array([ 96.38, 100., 82.45]), K_ab=array([ 173.51, 58.48]))[source]¶

Converts from Hunter L,a,b colour scale to CIE XYZ tristimulus values.

Parameters:	Lab (array_like) – Hunter L,a,b colour scale array. XYZ_n (array_like, optional) – Reference illuminant tristimulus values. K_ab (array_like, optional) – Reference illuminant chromaticity coefficients, if K_ab is set to None it will be computed using `XYZ_to_K_ab_HunterLab1966()`.
Returns:	CIE XYZ tristimulus values.
Return type:	ndarray

Notes

Input Lightness \(L^*\) is in domain [0, 100].
Input CIE XYZ and reference illuminant tristimulus values are in domain [0, 100].
Output CIE XYZ tristimulus values are in range [0, 100].

Examples

>>> Lab = np.array([31.74901573, -15.11462629, -2.78660758])
>>> D50 = HUNTERLAB_ILLUMINANTS[
...     'CIE 1931 2 Degree Standard Observer']['D50']
>>> Hunter_Lab_to_XYZ(Lab, D50.XYZ_n, D50.K_ab)   
array([  7.049534,  10.08    ,   9.558313])