colour.temperature.cct Module¶

Correlated Colour Temperature $T_{cp}$ ¶

Defines correlated colour temperature $T_{cp}$ computations objects:

uv_to_CCT_ohno2013(): Correlated colour temperature $T_{cp}$ and $\Delta_{uv}$ computation of given CIE UCS colourspace uv chromaticity coordinates using Yoshi Ohno (2013) method.
CCT_to_uv_ohno2013(): CIE UCS colourspace uv chromaticity coordinates computation of given correlated colour temperature $T_{cp}$ , $\Delta_{uv}$ using Yoshi Ohno (2013) method.
uv_to_CCT_robertson1968(): Correlated colour temperature $T_{cp}$ and $\Delta_{uv}$ computation of given CIE UCS colourspace uv chromaticity coordinates using Robertson (1968) method.
CCT_to_uv_robertson1968(): CIE UCS colourspace uv chromaticity coordinates computation of given correlated colour temperature $T_{cp}$ and $\Delta_{uv}$ using Robertson (1968) method.
xy_to_CCT_mccamy1992(): Correlated colour temperature $T_{cp}$ computation of given CIE XYZ colourspace xy chromaticity coordinates using McCamy (1992) method.
xy_to_CCT_hernandez1999(): Correlated colour temperature $T_{cp}$ computation of given CIE XYZ colourspace xy chromaticity coordinates using Hernandez-Andres, Lee & Romero (1999) method.
CCT_to_xy_kang2002(): CIE XYZ colourspace xy chromaticity coordinates computation of given correlated colour temperature $T_{cp}$ using Kang, Moon, Hong, Lee, Cho and Kim (2002) method.
CCT_to_xy_illuminant_D(): CIE XYZ colourspace xy chromaticity coordinates computation of CIE Illuminant D Series from given correlated colour temperature $T_{cp}$ of that CIE Illuminant D Series.

References

[1]	http://en.wikipedia.org/wiki/Color_temperature

colour.temperature.cct.PLANCKIAN_TABLE_TUVD¶: alias of PlanckianTable_Tuvdi

colour.temperature.cct.ROBERTSON_ISOTEMPERATURE_LINES_DATA = ((0, 0.18006, 0.26352, -0.24341), (10, 0.18066, 0.26589, -0.25479), (20, 0.18133, 0.26846, -0.26876), (30, 0.18208, 0.27119, -0.28539), (40, 0.18293, 0.27407, -0.3047), (50, 0.18388, 0.27709, -0.32675), (60, 0.18494, 0.28021, -0.35156), (70, 0.18611, 0.28342, -0.37915), (80, 0.1874, 0.28668, -0.40955), (90, 0.1888, 0.28997, -0.44278), (100, 0.19032, 0.29326, -0.47888), (125, 0.19462, 0.30141, -0.58204), (150, 0.19962, 0.30921, -0.70471), (175, 0.20525, 0.31647, -0.84901), (200, 0.21142, 0.32312, -1.0182), (225, 0.21807, 0.32909, -1.2168), (250, 0.22511, 0.33439, -1.4512), (275, 0.23247, 0.33904, -1.7298), (300, 0.2401, 0.34308, -2.0637), (325, 0.24792, 0.34655, -2.4681), (350, 0.25591, 0.34951, -2.9641), (375, 0.264, 0.352, -3.5814), (400, 0.27218, 0.35407, -4.3633), (425, 0.28039, 0.35577, -5.3762), (450, 0.28863, 0.35714, -6.7262), (475, 0.29685, 0.35823, -8.5955), (500, 0.30505, 0.35907, -11.324), (525, 0.3132, 0.35968, -15.628), (550, 0.32129, 0.36011, -23.325), (575, 0.32931, 0.36038, -40.77), (600, 0.33724, 0.36051, -116.45))¶

Robertson iso-temperature lines.

ROBERTSON_ISOTEMPERATURE_LINES_DATA : tuple: (Reciprocal Megakelvin, CIE 1960 Chromaticity Coordinate u, CIE 1960 Chromaticity Coordinate v, Slope)

Notes

A correction has been done by Bruce Lindbloom for 325 Megakelvin temperature: 0.24702 —> 0.24792

References

[2]	Wyszecki & Stiles, Color Science - Concepts and Methods Data and Formulae - Second Edition, Wiley Classics Library Edition, published 2000, ISBN-10: 0-471-39918-3, page 228.

colour.temperature.cct.ROBERTSON_ISOTEMPERATURE_LINES_RUVT¶: alias of WyszeckiRobertson_ruvt

colour.temperature.cct.planckian_table(uv, cmfs, start, end, count)[source]¶

Returns a planckian table from given CIE UCS colourspace uv chromaticity coordinates, colour matching functions and temperature range using Yoshi Ohno (2013) method.

Parameters:	uv (array_like) – uv chromaticity coordinates. cmfs (XYZ_ColourMatchingFunctions) – Standard observer colour matching functions. start (numeric) – Temperature range start in kelvins. end (numeric) – Temperature range end in kelvins. count (int) – Temperatures count in the planckian table.
Returns:	Planckian table.
Return type:	list

Examples

>>> from colour import STANDARD_OBSERVERS_CMFS
>>> from pprint import pprint
>>> cmfs = 'CIE 1931 2 Degree Standard Observer'
>>> cmfs = STANDARD_OBSERVERS_CMFS.get(cmfs)
>>> pprint(planckian_table((0.1978, 0.3122), cmfs, 1000, 1010, 10))    
[PlanckianTable_Tuvdi(Ti=1000.0, ui=0.4480108..., vi=0.3546249..., di=0.2537821...),
 PlanckianTable_Tuvdi(Ti=1001.1111111..., ui=0.4477508..., vi=0.3546475..., di=0.2535294...),
 PlanckianTable_Tuvdi(Ti=1002.2222222..., ui=0.4474910..., vi=0.3546700..., di=0.2532771...),
 PlanckianTable_Tuvdi(Ti=1003.3333333..., ui=0.4472316..., vi=0.3546924..., di=0.2530251...),
 PlanckianTable_Tuvdi(Ti=1004.4444444..., ui=0.4469724..., vi=0.3547148..., di=0.2527734...),
 PlanckianTable_Tuvdi(Ti=1005.5555555..., ui=0.4467136..., vi=0.3547372..., di=0.2525220...),
 PlanckianTable_Tuvdi(Ti=1006.6666666..., ui=0.4464550..., vi=0.3547595..., di=0.2522710...),
 PlanckianTable_Tuvdi(Ti=1007.7777777..., ui=0.4461968..., vi=0.3547817..., di=0.2520202...),
 PlanckianTable_Tuvdi(Ti=1008.8888888..., ui=0.4459389..., vi=0.3548040..., di=0.2517697...),
 PlanckianTable_Tuvdi(Ti=1010.0, ui=0.4456812..., vi=0.3548261..., di=0.2515196...)]

colour.temperature.cct.planckian_table_minimal_distance_index(planckian_table)[source]¶

Returns the shortest distance index in given planckian table using Yoshi Ohno (2013) method.

Parameters:	planckian_table (list) – Planckian table.
Returns:	Shortest distance index.
Return type:	int

Examples

>>> from colour import STANDARD_OBSERVERS_CMFS
>>> cmfs = 'CIE 1931 2 Degree Standard Observer'
>>> cmfs = STANDARD_OBSERVERS_CMFS.get(cmfs)
>>> table = planckian_table((0.1978, 0.3122), cmfs, 1000, 1010, 10)
>>> planckian_table_minimal_distance_index(table)
9

colour.temperature.cct.uv_to_CCT_ohno2013(uv, cmfs=<colour.colorimetry.cmfs.XYZ_ColourMatchingFunctions object at 0x102e0ccd0>, start=1000, end=100000, count=10, iterations=6)[source]¶

Returns the correlated colour temperature $T_{cp}$ and $\Delta_{uv}$ from given CIE UCS colourspace uv chromaticity coordinates, colour matching functions and temperature range using Yoshi Ohno (2013) method.

The iterations parameter defines the calculations precision: The higher its value, the more planckian tables will be generated through cascade expansion in order to converge to the exact solution.

Parameters:	uv (array_like) – CIE UCS colourspace uv chromaticity coordinates. cmfs (XYZ_ColourMatchingFunctions, optional) – Standard observer colour matching functions. start (numeric, optional) – Temperature range start in kelvins. end (numeric, optional) – Temperature range end in kelvins. count (int, optional) – Temperatures count in the planckian tables. iterations (int, optional) – Number of planckian tables to generate.
Returns:	Correlated colour temperature $T_{cp}$ , $\Delta_{uv}$ .
Return type:	tuple

References

[3]	Yoshi Ohno, Practical Use and Calculation of CCT and Duv, DOI: https://doi.org/10.1080/15502724.2014.839020

Examples

>>> from colour import STANDARD_OBSERVERS_CMFS
>>> cmfs = 'CIE 1931 2 Degree Standard Observer'
>>> cmfs = STANDARD_OBSERVERS_CMFS.get(cmfs)
>>> uv_to_CCT_ohno2013((0.1978, 0.3122), cmfs)  
(6507.5470349..., 0.0032236...)

colour.temperature.cct.CCT_to_uv_ohno2013(CCT, Duv=0, cmfs=<colour.colorimetry.cmfs.XYZ_ColourMatchingFunctions object at 0x102e0ccd0>)[source]¶

Returns the CIE UCS colourspace uv chromaticity coordinates from given correlated colour temperature $T_{cp}$ , $\Delta_{uv}$ and colour matching functions using Yoshi Ohno (2013) method.

Parameters:	CCT (numeric) – Correlated colour temperature $T_{cp}$ . Duv (numeric, optional) – $\Delta_{uv}$ . cmfs (XYZ_ColourMatchingFunctions, optional) – Standard observer colour matching functions.
Returns:	CIE UCS colourspace uv chromaticity coordinates.
Return type:	tuple

References

[4]	Yoshi Ohno, Practical Use and Calculation of CCT and Duv, DOI: https://doi.org/10.1080/15502724.2014.839020

Examples

>>> from colour import STANDARD_OBSERVERS_CMFS
>>> cmfs = 'CIE 1931 2 Degree Standard Observer'
>>> cmfs = STANDARD_OBSERVERS_CMFS.get(cmfs)
>>> CCT = 6507.4342201047066
>>> Duv = 0.003223690901512735
>>> CCT_to_uv_ohno2013(CCT, Duv, cmfs)  
(0.1978003..., 0.3122005...)

colour.temperature.cct.uv_to_CCT_robertson1968(uv)[source]¶

Returns the correlated colour temperature $T_{cp}$ and $\Delta_{uv}$ from given CIE UCS colourspace uv chromaticity coordinates using Robertson (1968) method.

Parameters:	uv (array_like) – CIE UCS colourspace uv chromaticity coordinates.
Returns:	Correlated colour temperature $T_{cp}$ , $\Delta_{uv}$ .
Return type:	tuple

References

[5]	Wyszecki & Stiles, Color Science - Concepts and Methods Data and Formulae - Second Edition, Wiley Classics Library Edition, published 2000, ISBN-10: 0-471-39918-3, page 227.

[6]	Adobe DNG SDK 1.3.0.0: dng_sdk_1_3/dng_sdk/source/dng_temperature.cpp: dng_temperature::Set_xy_coord.

Examples

>>> uv = (0.19374137599822966, 0.31522104394059397)
>>> uv_to_CCT_robertson1968(uv)  
(6500.0162879..., 0.0083333...)

colour.temperature.cct.CCT_to_uv_robertson1968(CCT, Duv=0)[source]¶

Returns the CIE UCS colourspace uv chromaticity coordinates from given correlated colour temperature $T_{cp}$ and $\Delta_{uv}$ using Robertson (1968) method.

Parameters:	CCT (numeric) – Correlated colour temperature $T_{cp}$ . Duv (numeric) – $\Delta_{uv}$ .
Returns:	CIE UCS colourspace uv chromaticity coordinates.
Return type:	tuple

References

[7]	Wyszecki & Stiles, Color Science - Concepts and Methods Data and Formulae - Second Edition, Wiley Classics Library Edition, published 2000, ISBN-10: 0-471-39918-3, page 227.

[8]	Adobe DNG SDK 1.3.0.0: dng_sdk_1_3/dng_sdk/source/dng_temperature.cpp: dng_temperature::xy_coord.

Examples

>>> CCT = 6500.0081378199056
>>> Duv = 0.0083333312442250979
>>> CCT_to_uv_robertson1968(CCT, Duv)  
(0.1937413..., 0.3152210...)

colour.temperature.cct.UV_TO_CCT_METHODS = CaseInsensitiveMapping({u'Ohno 2013': <function uv_to_CCT_ohno2013 at 0x102fdb938>, u'robertson1968': <function uv_to_CCT_robertson1968 at 0x102fdba28>, u'ohno2013': <function uv_to_CCT_ohno2013 at 0x102fdb938>, u'Robertson 1968': <function uv_to_CCT_robertson1968 at 0x102fdba28>})¶

Supported CIE UCS colourspace uv chromaticity coordinates to correlated colour temperature $T_{cp}$ computation methods.

UV_TO_CCT_METHODS : dict: (‘Ohno 2013’, ‘Robertson 1968’)

Aliases:

‘ohno2013’: ‘Ohno 2013’
‘robertson1968’: ‘Robertson 1968’

colour.temperature.cct.uv_to_CCT(uv, method=u'Ohno 2013', **kwargs)[source]¶

Returns the correlated colour temperature $T_{cp}$ and $\Delta_{uv}$ from given CIE UCS colourspace uv chromaticity coordinates using given method.

Parameters:	uv (array_like) – CIE UCS colourspace uv chromaticity coordinates. method (unicode) – (‘Ohno 2013’, ‘Robertson 1968’) Computation method. kwargs () – Keywords arguments.
Returns:	Correlated colour temperature $T_{cp}$ , $\Delta_{uv}$ .
Return type:	tuple
Raises:	`ValueError` – If the computation method is not defined.

Examples

>>> from colour import STANDARD_OBSERVERS_CMFS
>>> cmfs = 'CIE 1931 2 Degree Standard Observer'
>>> cmfs = STANDARD_OBSERVERS_CMFS.get(cmfs)
>>> uv_to_CCT((0.1978, 0.3122), cmfs=cmfs)  
(6507.5470349..., 0.0032236...)

colour.temperature.cct.CCT_TO_UV_METHODS = CaseInsensitiveMapping({u'Ohno 2013': <function CCT_to_uv_ohno2013 at 0x102fdb9b0>, u'robertson1968': <function CCT_to_uv_robertson1968 at 0x102fdbaa0>, u'ohno2013': <function CCT_to_uv_ohno2013 at 0x102fdb9b0>, u'Robertson 1968': <function CCT_to_uv_robertson1968 at 0x102fdbaa0>})¶

Supported correlated colour temperature $T_{cp}$ to CIE UCS colourspace uv chromaticity coordinates computation methods.

CCT_TO_UV_METHODS : dict: (‘Ohno 2013’, ‘Robertson 1968’)

Aliases:

‘ohno2013’: ‘Ohno 2013’
‘robertson1968’: ‘Robertson 1968’

colour.temperature.cct.CCT_to_uv(CCT, Duv=0, method=u'Ohno 2013', **kwargs)[source]¶

Returns the CIE UCS colourspace uv chromaticity coordinates from given correlated colour temperature $T_{cp}$ and $\Delta_{uv}$ using given method.

Parameters:	CCT (numeric) – Correlated colour temperature $T_{cp}$ . Duv (numeric) – $\Delta_{uv}$ . method (unicode) – (‘Ohno 2013’, ‘Robertson 1968’) Computation method. kwargs () – Keywords arguments.
Returns:	CIE UCS colourspace uv chromaticity coordinates.
Return type:	tuple
Raises:	`ValueError` – If the computation method is not defined.

Examples

>>> from colour import STANDARD_OBSERVERS_CMFS
>>> cmfs = 'CIE 1931 2 Degree Standard Observer'
>>> cmfs = STANDARD_OBSERVERS_CMFS.get(cmfs)
>>> CCT = 6507.4342201047066
>>> Duv = 0.003223690901512735
>>> CCT_to_uv(CCT, Duv, cmfs=cmfs)  
(0.1978003..., 0.3122005...)

colour.temperature.cct.xy_to_CCT_mccamy1992(xy)[source]¶

Returns the correlated colour temperature $T_{cp}$ from given CIE XYZ colourspace xy chromaticity coordinates using McCamy (1992) method.

Parameters:	xy (array_like) – xy chromaticity coordinates.
Returns:	Correlated colour temperature $T_{cp}$ .
Return type:	numeric

References

[9]	http://en.wikipedia.org/wiki/Color_temperature#Approximation (Last accessed 28 June 2014)

Examples

>>> xy_to_CCT_mccamy1992((0.31271, 0.32902))  
6504.3893830...

colour.temperature.cct.xy_to_CCT_hernandez1999(xy)[source]¶

Returns the correlated colour temperature $T_{cp}$ from given CIE XYZ colourspace xy chromaticity coordinates using Hernandez-Andres, Lee & Romero (1999) method.

Parameters:	xy (array_like) – xy chromaticity coordinates.
Returns:	Correlated colour temperature $T_{cp}$ .
Return type:	numeric

References

[10]	Calculating correlated color temperatures across the entire gamut of daylight and skylight chromaticities, DOI: https://doi.org/10.1364/AO.38.005703

Examples

>>> xy_to_CCT_hernandez1999((0.31271, 0.32902))  
6500.0421533...

colour.temperature.cct.CCT_to_xy_kang2002(CCT)[source]¶

Returns the CIE XYZ colourspace xy chromaticity coordinates from given correlated colour temperature $T_{cp}$ using Kang, Moon, Hong, Lee, Cho and Kim (2002) method.

Parameters:	CCT (numeric) – Correlated colour temperature $T_{cp}$ .
Returns:	xy chromaticity coordinates.
Return type:	tuple
Raises:	`ValueError` – If the correlated colour temperature is not in appropriate domain.

References

[11]	Design of Advanced Color - Temperature Control System for HDTV Applications

Examples

>>> CCT_to_xy_kang2002(6504.38938305)  
(0.3134259..., 0.3235959...)

colour.temperature.cct.CCT_to_xy_illuminant_D(CCT)[source]¶

Converts from the correlated colour temperature $T_{cp}$ of a CIE Illuminant D Series to the chromaticity of that CIE Illuminant D Series.

Parameters:	CCT (numeric) – Correlated colour temperature $T_{cp}$ .
Returns:	xy chromaticity coordinates.
Return type:	tuple
Raises:	`ValueError` – If the correlated colour temperature is not in appropriate domain.

References

[12]	Wyszecki & Stiles, Color Science - Concepts and Methods Data and Formulae - Second Edition, Wiley Classics Library Edition, published 2000, ISBN-10: 0-471-39918-3, page 145.

Examples

>>> CCT_to_xy_illuminant_D(6504.38938305)  
(0.3127077..., 0.3291128...)

colour.temperature.cct.XY_TO_CCT_METHODS = CaseInsensitiveMapping({u'hernandez1999': <function xy_to_CCT_hernandez1999 at 0x102fdbc80>, u'Hernandez 1999': <function xy_to_CCT_hernandez1999 at 0x102fdbc80>, u'McCamy 1992': <function xy_to_CCT_mccamy1992 at 0x102fdbc08>, u'mccamy1992': <function xy_to_CCT_mccamy1992 at 0x102fdbc08>})¶

Supported CIE XYZ colourspace xy chromaticity coordinates to correlated colour temperature $T_{cp}$ computation methods.

XY_TO_CCT_METHODS : dict: (‘McCamy 1992’, ‘Hernandez 1999’)

Aliases:

‘mccamy1992’: ‘McCamy 1992’
‘hernandez1999’: ‘Hernandez 1999’

colour.temperature.cct.xy_to_CCT(xy, method=u'McCamy 1992', **kwargs)[source]¶

Returns the correlated colour temperature $T_{cp}$ from given CIE XYZ colourspace xy chromaticity coordinates using given method.

Parameters:	xy (array_like) – xy chromaticity coordinates. method (unicode (‘McCamy 1992’, ‘Hernandez 1999’)) – Computation method. kwargs () – Keywords arguments.
Returns:	Correlated colour temperature $T_{cp}$ .
Return type:	numeric

colour.temperature.cct.CCT_TO_XY_METHODS = CaseInsensitiveMapping({u'cie_d': <function CCT_to_xy_illuminant_D at 0x102fdbd70>, u'CIE Illuminant D Series': <function CCT_to_xy_illuminant_D at 0x102fdbd70>, u'kang2002': <function CCT_to_xy_kang2002 at 0x102fdbcf8>, u'Kang 2002': <function CCT_to_xy_kang2002 at 0x102fdbcf8>})¶

Supported correlated colour temperature $T_{cp}$ to CIE XYZ colourspace xy chromaticity coordinates computation methods.

CCT_TO_XY_METHODS : dict: (‘Kang 2002’, ‘CIE Illuminant D Series’)

Aliases:

‘kang2002’: ‘Kang 2002’
‘cie_d’: ‘Hernandez 1999’

colour.temperature.cct.CCT_to_xy(CCT, method=u'Kang 2002')[source]¶

Returns the CIE XYZ colourspace xy chromaticity coordinates from given correlated colour temperature $T_{cp}$ using given method.

Parameters:	CCT (numeric) – Correlated colour temperature $T_{cp}$ . method (unicode (‘Kang 2002’, ‘CIE Illuminant D Series’)) – Computation method.
Returns:	xy chromaticity coordinates.
Return type:	tuple

colour.temperature.cct Module¶

Correlated Colour Temperature TcpT_{cp}¶

Correlated Colour Temperature $T_{cp}$ ¶