# colour.colorimetry.yellowness Module¶

## Yellowness Index $$Y$$¶

Defines yellowness index $$Y$$ computation objects:

References

 [1] (1, 2) X-Rite, & Pantone. (2012). Color iQC and Color iMatch Color Calculations Guide. Retrieved from http://www.xrite.com/documents/literature/en/09_Color_Calculations_en.pdf
colour.colorimetry.yellowness.yellowness_ASTMD1925(XYZ)[source]

Returns the yellowness index $$YI$$ of given sample CIE XYZ tristimulus values using ASTM D1925 method. [1]

ASTM D1925 has been specifically developed for the definition of the Yellowness of homogeneous, non-fluorescent, almost neutral-transparent, white-scattering or opaque plastics as they will be reviewed under daylight condition. It can be other materials as well, as long as they fit into this description.

Parameters: XYZ (array_like) – CIE XYZ tristimulus values of sample. Whiteness $$YI$$. numeric or ndarray

Notes

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

Warning

The input domain of that definition is non standard!

Examples

>>> import numpy as np
>>> XYZ = np.array([95.00000000, 100.00000000, 105.00000000])
>>> yellowness_ASTMD1925(XYZ)
10.2999999...

colour.colorimetry.yellowness.yellowness_ASTME313(XYZ)[source]

Returns the yellowness index $$YI$$ of given sample CIE XYZ tristimulus values using ASTM E313 method. [1]

ASTM E313 has successfully been used for a variety of white or near white materials. This includes coatings, Plastics, Textiles.

Parameters: XYZ (array_like) – CIE XYZ tristimulus values of sample. Whiteness $$YI$$. numeric or ndarray

Notes

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

Warning

The input domain of that definition is non standard!

Examples

>>> import numpy as np
>>> XYZ = np.array([95.00000000, 100.00000000, 105.00000000])
>>> yellowness_ASTME313(XYZ)
11.0650000...

colour.colorimetry.yellowness.YELLOWNESS_METHODS = CaseInsensitiveMapping({u'ASTM E313': <function yellowness_ASTME313>, u'ASTM D1925': <function yellowness_ASTMD1925>})

Supported yellowness computations methods.

YELLOWNESS_METHODS : CaseInsensitiveMapping
{‘ASTM E313’, ‘ASTM D1925’}
colour.colorimetry.yellowness.yellowness(XYZ, method=u'ASTM E313')[source]

Returns the yellowness $$W$$ using given method.

Parameters: XYZ (array_like) – CIE XYZ tristimulus values of sample. method (unicode, optional) – {‘ASTM E313’, ‘ASTM D1925’}, Computation method. yellowness $$Y$$. numeric or ndarray

Examples

>>> import numpy as np
>>> XYZ = np.array([95.00000000, 100.00000000, 105.00000000])
>>> yellowness(XYZ)
11.0650000...
>>> method = 'ASTM D1925'
>>> yellowness(XYZ, method=method)
10.2999999...