colour.quality.cqs Module¶
Colour Quality Scale¶
Defines colour quality scale computation objects:
References
[1] | Davis, W., & Ohno, Y. (2010). Color quality scale. Optical Engineering, 49(3), 33602–33616. doi:10.1117/1.3360335 |
[2] | Ohno, Y., & Davis, W. (2008). NIST CQS simulation 7.4. Retrieved from http://cie2.nist.gov/TC1-69/NIST CQS simulation 7.4.xls |
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class
colour.quality.cqs.
VS_ColorimetryData
[source]¶ Bases:
colour.quality.cqs.VS_ColorimetryData
Defines the the class holding VS test colour samples colorimetry data.
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class
colour.quality.cqs.
VS_ColourQualityScaleData
[source]¶ Bases:
colour.quality.cqs.VS_ColourQualityScaleData
Defines the the class holding VS test colour samples colour quality scale data.
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class
colour.quality.cqs.
CQS_Specification
[source]¶ Bases:
colour.quality.cqs.CQS_Specification
Defines the CQS colour quality specification.
Parameters: - name (unicode) – Name of the test spectral power distribution.
- Q_a (numeric) – Colour quality scale \(Q_a\).
- Q_f (numeric) – Colour fidelity scale \(Q_f\) intended to evaluate the fidelity of object colour appearances (compared to the reference illuminant of the same correlated colour temperature and illuminance).
- Q_p (numeric) – Colour preference scale \(Q_p\) similar to colour quality scale \(Q_a\) but placing additional weight on preference of object colour appearance. This metric is based on the notion that increases in chroma are generally preferred and should be rewarded.
- Q_g (numeric) – Gamut area scale \(Q_g\) representing the relative gamut formed by the (\(a^*\), \(b^*\)) coordinates of the 15 samples illuminated by the test light source in the CIE LAB object colourspace.
- Q_d (numeric) – Relative gamut area scale \(Q_d\).
- Q_as (dict) – Individual CQS data for each sample.
- colorimetry_data (tuple) – Colorimetry data for the test and reference computations.
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colour.quality.cqs.
colour_quality_scale
(spd_test, additional_data=False)[source]¶ Returns the colour quality scale of given spectral power distribution.
Parameters: - spd_test (SpectralPowerDistribution) – Test spectral power distribution.
- additional_data (bool, optional) – Output additional data.
Returns: Color quality scale.
Return type: numeric or CQS_Specification
Examples
>>> from colour import ILLUMINANTS_RELATIVE_SPDS >>> spd = ILLUMINANTS_RELATIVE_SPDS.get('F2') >>> colour_quality_scale(spd) 64.6860580...
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colour.quality.cqs.
gamut_area
(Lab)[source]¶ Returns the gamut area \(G\) covered by given CIE Lab matrices.
Parameters: Lab (array_like) – CIE Lab colourspace matrices. Returns: Gamut area \(G\). Return type: numeric Examples
>>> Lab = [ ... np.array([39.94996006, 34.59018231, -19.86046321]), ... np.array([38.88395498, 21.44348519, -34.87805301]), ... np.array([36.60576301, 7.06742454, -43.21461177]), ... np.array([46.60142558, -15.90481586, -34.64616865]), ... np.array([56.50196523, -29.54655550, -20.50177194]), ... np.array([55.73912101, -43.39520959, -5.08956953]), ... np.array([56.20776870, -53.68997662, 20.21134410]), ... np.array([66.16683122, -38.64600327, 42.77396631]), ... np.array([76.72952110, -23.92148210, 61.04740432]), ... np.array([82.85370708, -3.98679065, 75.43320144]), ... np.array([69.26458861, 13.11066359, 68.83858372]), ... np.array([69.63154351, 28.24532497, 59.45609803]), ... np.array([61.26281449, 40.87950839, 44.97606172]), ... np.array([41.62567821, 57.34129516, 27.46718170]), ... np.array([40.52565174, 48.87449192, 3.45121680])] >>> gamut_area(Lab) 8335.9482018...
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colour.quality.cqs.
vs_colorimetry_data
(spd_test, spd_reference, spds_vs, cmfs, chromatic_adaptation=False)[source]¶ Returns the VS test colour samples colorimetry data.
Parameters: - spd_test (SpectralPowerDistribution) – Test spectral power distribution.
- spd_reference (SpectralPowerDistribution) – Reference spectral power distribution.
- spds_vs (dict) – VS test colour samples spectral power distributions.
- cmfs (XYZ_ColourMatchingFunctions) – Standard observer colour matching functions.
- chromatic_adaptation (bool, optional) – Perform chromatic adaptation.
Returns: VS test colour samples colorimetry data.
Return type:
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colour.quality.cqs.
CCT_factor
(reference_data, XYZ_r)[source]¶ Returns the correlated colour temperature factor penalizing lamps with extremely low correlated colour temperatures.
Parameters: - reference_data (VS_ColorimetryData) – Reference colorimetry data.
- XYZ_r (array_like) – CIE XYZ tristimulus values for reference.
Returns: Correlated colour temperature factor.
Return type: numeric
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colour.quality.cqs.
scale_conversion
(D_E_ab, CCT_f, scaling_f=3.104)[source]¶ Returns the colour quality scale for given \(\Delta E_{ab}\) value and given correlated colour temperature penalizing factor.
Parameters: - D_E_ab (numeric) – \(\Delta E_{ab}\) value.
- CCT_f (numeric) – Correlated colour temperature penalizing factor.
- scaling_f (numeric, optional) – Scaling factor constant.
Returns: Colour quality scale.
Return type: numeric
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colour.quality.cqs.
delta_E_RMS
(cqs_data, attribute)[source]¶ Computes the root-mean-square average for given CQS data.
Parameters: - cqs_data (VS_ColourQualityScaleData) – CQS data.
- attribute (unicode) – Colorimetry data attribute to use to compute the root-mean-square average.
Returns: Root-mean-square average.
Return type: numeric