Colorimetry

Spectral Data Structure

colour

SpectralPowerDistribution([data, domain]) Defines the spectral power distribution: the base object for spectral computations.
MultiSpectralPowerDistribution([data, …]) Defines multi-spectral power distribution: the base object for multi spectral computations.
SpectralShape([start, end, interval]) Defines the base object for spectral power distribution shape.
DEFAULT_SPECTRAL_SHAPE Default spectral shape according to ASTM E308-15 practise shape.
ASTME30815_PRACTISE_SHAPE Shape for *ASTM E308-15 practise* – (360, 780, 1).

Spectral Data Generation

colour

blackbody_spd(temperature[, shape, c1, c2, n]) Returns the spectral power distribution of the planckian radiator for given temperature \(T[K]\).
CIE_standard_illuminant_A_function(wl) CIE Standard Illuminant A is intended to represent typical, domestic, tungsten-filament lighting.
D_illuminant_relative_spd(xy[, M1_M2_rounding]) Returns the relative spectral power distribution of given CIE Standard Illuminant D Series using given xy chromaticity coordinates.
constant_spd(k[, shape, dtype]) Returns a spectral power distribution of given spectral shape filled with constant \(k\) values.
ones_spd([shape]) Returns a spectral power distribution of given spectral shape filled with ones.
zeros_spd([shape]) Returns a spectral power distribution of given spectral shape filled with zeros.

colour.colorimetry

blackbody_spectral_radiance(wavelength, …) Returns the spectral radiance of a blackbody at thermodynamic temperature \(T[K]\) in a medium having index of refraction \(n\).
planck_law(wavelength, temperature[, c1, c2, n]) Returns the spectral radiance of a blackbody at thermodynamic temperature \(T[K]\) in a medium having index of refraction \(n\).

Conversion to Tristimulus Values

colour

spectral_to_XYZ(spd[, cmfs, illuminant, method]) Converts given spectral power distribution to CIE XYZ tristimulus values using given colour matching functions, illuminant and method.
SPECTRAL_TO_XYZ_METHODS Supported spectral power distribution to CIE XYZ tristimulus values conversion methods
multi_spectral_to_XYZ(msa[, shape, cmfs, …]) Converts given multi-spectral array \(msa\) with given spectral shape to CIE XYZ tristimulus values using given colour matching functions and illuminant.
MULTI_SPECTRAL_TO_XYZ_METHODS Supported multi spectral array to CIE XYZ tristimulus values conversion methods.
wavelength_to_XYZ(wavelength[, cmfs]) Converts given wavelength \(\lambda\) to CIE XYZ tristimulus values using given colour matching functions.

ASTM E308-15

colour.colorimetry

spectral_to_XYZ_ASTME30815(spd[, cmfs, …]) Converts given spectral power distribution to CIE XYZ tristimulus values using given colour matching functions and illuminant according to practise ASTM E308-15 method.

Ancillary Objects

colour.colorimetry

spectral_to_XYZ_tristimulus_weighting_factors_ASTME30815(spd) Converts given spectral power distribution to CIE XYZ tristimulus values using given colour matching functions and illuminant using a table of tristimulus weighting factors according to practise ASTM E308-15 method.
adjust_tristimulus_weighting_factors_ASTME30815(W, …) Adjusts given table of tristimulus weighting factors to account for a shorter wavelengths range of the test spectral shape compared to the reference spectral shape using practise ASTM E308-15 method: Weights at the wavelengths for which data are not available are added to the weights at the shortest and longest wavelength for which spectral data are available.
lagrange_coefficients_ASTME202211([…]) Computes the Lagrange Coefficients for given interval size using practise ASTM E2022-11 method.
tristimulus_weighting_factors_ASTME202211(…) Returns a table of tristimulus weighting factors for given colour matching functions and illuminant using practise ASTM E2022-11 method.

Integration

colour.colorimetry

spectral_to_XYZ_integration(spd[, cmfs, …]) Converts given spectral power distribution to CIE XYZ tristimulus values using given colour matching functions and illuminant according to classical integration method.
multi_spectral_to_XYZ_integration(msa, shape) Converts given multi-spectral array \(msa\) with given spectral shape to CIE XYZ tristimulus values using given colour matching functions and illuminant.

Spectral Bandpass Dependence Correction

colour

bandpass_correction(spd[, method]) Implements spectral bandpass dependence correction on given spectral power distribution using given method.
BANDPASS_CORRECTION_METHODS Supported spectral bandpass dependence correction methods.

Stearns and Stearns (1988)

colour.colorimetry

bandpass_correction_Stearns1988(spd) Implements spectral bandpass dependence correction on given spectral power distribution using Stearns and Stearns (1988) method.

Colour Matching Functions

colour.colorimetry

LMS_ConeFundamentals([data, domain, labels]) Implements support for the Stockman and Sharpe LMS cone fundamentals colour matching functions.
RGB_ColourMatchingFunctions([data, domain, …]) Implements support for the CIE RGB colour matching functions.
XYZ_ColourMatchingFunctions([data, domain, …]) Implements support for the CIE Standard Observers XYZ colour matching functions.

Dataset

colour

CMFS Aggregated colour matching functions.
LMS_CMFS LMS colour matching functions.
RGB_CMFS CIE RGB colour matching functions.
STANDARD_OBSERVERS_CMFS CIE Standard Observers XYZ colour matching functions.

Colour Matching Functions Transformations

Ancillary Objects

colour.colorimetry

RGB_2_degree_cmfs_to_XYZ_2_degree_cmfs(…) Converts Wright & Guild 1931 2 Degree RGB CMFs colour matching functions into the CIE 1931 2 Degree Standard Observer colour matching functions.
RGB_10_degree_cmfs_to_XYZ_10_degree_cmfs(…) Converts Stiles & Burch 1959 10 Degree RGB CMFs colour matching functions into the CIE 1964 10 Degree Standard Observer colour matching functions.
RGB_10_degree_cmfs_to_LMS_10_degree_cmfs(…) Converts Stiles & Burch 1959 10 Degree RGB CMFs colour matching functions into the Stockman & Sharpe 10 Degree Cone Fundamentals spectral sensitivity functions.
LMS_2_degree_cmfs_to_XYZ_2_degree_cmfs(…) Converts Stockman & Sharpe 2 Degree Cone Fundamentals colour matching functions into the CIE 2012 2 Degree Standard Observer colour matching functions.
LMS_10_degree_cmfs_to_XYZ_10_degree_cmfs(…) Converts Stockman & Sharpe 10 Degree Cone Fundamentals colour matching functions into the CIE 2012 10 Degree Standard Observer colour matching functions.

Illuminants and Light Sources

Dataset

colour

ILLUMINANTS Aggregated CIE illuminants chromaticity coordinates.
ILLUMINANTS_SPDS CIE illuminants relative spectral power distributions.
HUNTERLAB_ILLUMINANTS Aggregated Hunter L,a,b illuminant dataset.
LIGHT_SOURCES Aggregated light sources chromaticity coordinates.
LIGHT_SOURCES_SPDS Aggregated light sources spectral power distributions.

Dominant Wavelength and Purity

colour

dominant_wavelength(xy, xy_n[, cmfs, reverse]) Returns the dominant wavelength \(\lambda_d\) for given colour stimulus \(xy\) and the related \(xy_wl\) first and \(xy_{cw}\) second intersection coordinates with the spectral locus.
complementary_wavelength(xy, xy_n[, cmfs]) Returns the complementary wavelength \(\lambda_c\) for given colour stimulus \(xy\) and the related \(xy_wl\) first and \(xy_{cw}\) second intersection coordinates with the spectral locus.
excitation_purity(xy, xy_n[, cmfs]) Returns the excitation purity \(P_e\) for given colour stimulus \(xy\).
colorimetric_purity(xy, xy_n[, cmfs]) Returns the colorimetric purity \(P_c\) for given colour stimulus \(xy\).

Luminous Efficiency Functions

colour

luminous_efficacy(spd[, lef]) Returns the luminous efficacy in \(lm\cdot W^{-1}\) of given spectral power distribution using given luminous efficiency function.
luminous_efficiency(spd[, lef]) Returns the luminous efficiency of given spectral power distribution using given luminous efficiency function.
luminous_flux(spd[, lef, K_m]) Returns the luminous flux for given spectral power distribution using given luminous efficiency function.
mesopic_luminous_efficiency_function(Lp[, …]) Returns the mesopic luminous efficiency function \(V_m(\lambda)\) for given photopic luminance \(L_p\).

Dataset

colour

LEFS Aggregated luminous efficiency functions.
PHOTOPIC_LEFS Photopic luminous efficiency functions.
SCOTOPIC_LEFS Scotopic luminous efficiency functions.

Lightness Computation

colour

lightness(Y[, method]) Returns the Lightness \(L\) using given method.
LIGHTNESS_METHODS Supported Lightness computations methods.

Glasser, Mckinney, Reilly and Schnelle (1958)

colour.colorimetry

lightness_Glasser1958(Y) Returns the Lightness \(L\) of given luminance \(Y\) using Glasser et alii (1958) method.

Wyszecki (1963)

colour.colorimetry

lightness_Wyszecki1963(Y) Returns the Lightness \(W\) of given luminance \(Y\) using Wyszecki (1963) method.

CIE 1976

colour.colorimetry

lightness_CIE1976(Y[, Y_n]) Returns the Lightness \(L^*\) of given luminance \(Y\) using given reference white luminance \(Y_n\) as per CIE 1976 recommendation.

Fairchild and Wyble (2010)

colour.colorimetry

lightness_Fairchild2010(Y[, epsilon]) Computes Lightness \(L_{hdr}\) of given luminance \(Y\) using Fairchild and Wyble (2010) method according to Michealis-Menten kinetics.

Fairchild and Chen (2011)

colour.colorimetry

lightness_Fairchild2011(Y[, epsilon, method]) Computes Lightness \(L_{hdr}\) of given luminance \(Y\) using Fairchild and Chen (2011) method accordingly to Michealis-Menten kinetics.

Luminance Computation

colour

luminance(LV[, method]) Returns the luminance \(Y\) of given Lightness \(L^*\) or given Munsell value \(V\).
LUMINANCE_METHODS Supported luminance computations methods.

Newhall, Nickerson and Judd (1943)

colour.colorimetry

luminance_Newhall1943(V) Returns the luminance \(R_Y\) of given Munsell value \(V\) using Newhall et alii (1943) method.

CIE 1976

colour.colorimetry

luminance_CIE1976(Lstar[, Y_n]) Returns the luminance \(Y\) of given Lightness \(L^*\) with given reference white luminance \(Y_n\).

ASTM D1535-08e1

colour.colorimetry

luminance_ASTMD153508(V) Returns the luminance \(Y\) of given Munsell value \(V\) using ASTM D1535-08e1 method.

Fairchild and Wyble (2010)

colour.colorimetry

luminance_Fairchild2010(L_hdr[, epsilon]) Computes luminance \(Y\) of given Lightness \(L_{hdr}\) using Fairchild and Wyble (2010) method according to Michealis-Menten kinetics.

Fairchild and Chen (2011)

colour.colorimetry

luminance_Fairchild2011(L_hdr[, epsilon, method]) Computes luminance \(Y\) of given Lightness \(L_{hdr}\) using Fairchild and Chen (2011) method accordingly to Michealis-Menten kinetics.

Whiteness Computation

colour

whiteness([method]) Returns the whiteness \(W\) using given method.
WHITENESS_METHODS Supported whiteness computations methods.

Berger (1959)

colour.colorimetry

whiteness_Berger1959(XYZ, XYZ_0) Returns the whiteness index \(WI\) of given sample CIE XYZ tristimulus values using Berger (1959) method.

Taube (1960)

colour.colorimetry

whiteness_Taube1960(XYZ, XYZ_0) Returns the whiteness index \(WI\) of given sample CIE XYZ tristimulus values using Taube (1960) method.

Stensby (1968)

colour.colorimetry

whiteness_Stensby1968(Lab) Returns the whiteness index \(WI\) of given sample CIE L*a*b* colourspace array using Stensby (1968) method.

ASTM E313

colour.colorimetry

whiteness_ASTME313(XYZ) Returns the whiteness index \(WI\) of given sample CIE XYZ tristimulus values using ASTM E313 method.

Ganz and Griesser (1979)

colour.colorimetry

whiteness_Ganz1979(xy, Y) Returns the whiteness index \(W\) and tint \(T\) of given sample xy chromaticity coordinates using Ganz and Griesser (1979) method.

CIE 2004

colour.colorimetry

whiteness_CIE2004(xy, Y, xy_n[, observer]) Returns the whiteness \(W\) or \(W_{10}\) and tint \(T\) or \(T_{10}\) of given sample xy chromaticity coordinates using CIE 2004 method.

Yellowness Computation

colour

yellowness(XYZ[, method]) Returns the yellowness \(W\) using given method.
YELLOWNESS_METHODS Supported yellowness computations methods.

ASTM D1925

colour.colorimetry

yellowness_ASTMD1925(XYZ) Returns the yellowness index \(YI\) of given sample CIE XYZ tristimulus values using ASTM D1925 method.

ASTM E313

colour.colorimetry

yellowness_ASTME313(XYZ) Returns the yellowness index \(YI\) of given sample CIE XYZ tristimulus values using ASTM E313 method.