colour.excitation_purity#

colour.excitation_purity(xy: ArrayLike, xy_n: ArrayLike, cmfs: MultiSpectralDistributions | None = None) → NDArrayFloat[source]#

Return the excitation purity \(P_e\) for given colour stimulus \(xy\).

Parameters:

xy (ArrayLike) – Colour stimulus CIE xy chromaticity coordinates.
xy_n (ArrayLike) – Achromatic stimulus CIE xy chromaticity coordinates.
cmfs (MultiSpectralDistributions | None) – Standard observer colour matching functions, default to the CIE 1931 2 Degree Standard Observer.

Returns:

Excitation purity \(P_e\).

Return type:

np.float or numpy.ndarray

References

[CIET14804b], [Erdb]

Examples

>>> from colour.colorimetry import MSDS_CMFS
>>> cmfs = MSDS_CMFS["CIE 1931 2 Degree Standard Observer"]
>>> xy = np.array([0.54369557, 0.32107944])
>>> xy_n = np.array([0.31270000, 0.32900000])
>>> excitation_purity(xy, xy_n, cmfs)  
0.6228856...