colour.models.cie_lab Module¶

CIE Lab Colourspace¶

Defines the CIE Lab colourspace transformations:

• XYZ_to_Lab()
• Lab_to_XYZ()
• Lab_to_LCHab()
• LCHab_to_Lab()

References

colour.models.cie_lab.XYZ_to_Lab(XYZ, illuminant=(0.34567, 0.3585))[source]¶

Converts from CIE XYZ colourspace to CIE Lab colourspace.

Parameters:	XYZ (array_like, (3,)) – CIE XYZ colourspace matrix. illuminant (array_like, optional) – Reference illuminant chromaticity coordinates.
Returns:	CIE Lab colourspace matrix.
Return type:	ndarray, (3,)

Notes

• Input CIE XYZ is in domain [0, 1].
• Input illuminant chromaticity coordinates are in domain [0, 1].
• Output Lightness $L^*$ is in domain [0, 100].

References

[2]	http://www.brucelindbloom.com/Eqn_XYZ_to_Lab.html (Last accessed 24 February 2014)

Examples

>>> XYZ_to_Lab(np.array([0.92193107, 1, 1.03744246]))  
array([ 100.        ,   -7.4178784...,  -15.8574210...])

colour.models.cie_lab.Lab_to_XYZ(Lab, illuminant=(0.34567, 0.3585))[source]¶

Converts from CIE Lab colourspace to CIE XYZ colourspace.

Parameters:	Lab (array_like, (3,)) – CIE Lab colourspace matrix. illuminant (array_like, optional) – Reference illuminant chromaticity coordinates.
Returns:	CIE XYZ colourspace matrix.
Return type:	ndarray, (3,)

Notes

• Input Lightness $L^*$ is in domain [0, 100].
• Input illuminant chromaticity coordinates are in domain [0, 1].
• Output CIE XYZ colourspace matrix is in domain [0, 1].

References

[3]	http://www.brucelindbloom.com/Eqn_Lab_to_XYZ.html (Last accessed 24 February 2014)

Examples

>>> Lab = np.array([100, -7.41787844, -15.85742105])
>>> Lab_to_XYZ(Lab)  
array([ 0.9219310...,  1.        ,  1.0374424...])

colour.models.cie_lab.Lab_to_LCHab(Lab)[source]¶

Converts from CIE Lab colourspace to CIE LCHab colourspace.

Parameters:	Lab (array_like, (3,)) – CIE Lab colourspace matrix.
Returns:	CIE LCHab colourspace matrix.
Return type:	ndarray, (3,)

Notes

• Lightness $L^*$ is in domain [0, 100].

References

[4]	http://www.brucelindbloom.com/Eqn_Lab_to_LCH.html (Last accessed 24 February 2014)

Examples

>>> Lab = np.array([100, -7.41787844, -15.85742105])
>>> Lab_to_LCHab(Lab)  
array([ 100.        ,   17.5066479...,  244.9304684...])

colour.models.cie_lab.LCHab_to_Lab(LCHab)[source]¶

Converts from CIE LCHab colourspace to CIE Lab colourspace.

Parameters:	LCHab (array_like, (3,)) – CIE LCHab colourspace matrix.
Returns:	CIE Lab colourspace matrix.
Return type:	ndarray, (3,)

Notes

• Lightness $L^*$ is in domain [0, 100].

References

[5]	http://www.brucelindbloom.com/Eqn_LCH_to_Lab.html (Last accessed 24 February 2014)

Examples

>>> LCHab = np.array([100, 17.50664796, 244.93046842])
>>> LCHab_to_Lab(LCHab)  
array([ 100.        ,   -7.4178784...,  -15.8574210...])