Introduction¶

Names and acronyms¶

SPD: spectrual power distribution. This is a function of wavelength $\lambda$ , and describes the power per unit area per unit wavelength of an illumination.

CMF: color matching function. This is a function of wavelength $\lambda$ describing the chromatic response of the “observer”. A CMF $\bar{x}(\cdot)$ will have response $\bar{x}(\lambda)$ at a unit-power light of single wavelength $\lambda$ , and given a spectral power distribution $I(\lambda)$ , the response will be $X = \int I(\lambda) \bar{x}(\lambda) d\lambda$ .

Note that SPD and CMF should not be mistaken with each another. For example, the CIE-RGB color space uses three monochromatic (single-wavelength) primary colors, which means their SPDs are delta functions, but their CMFs are not.

LMS: a color space represented by the response of three types of cones of the human eye.

WL: wavelength list. This is a 1D ndarray with equally-spaced entries in increasing order. The wavelength entries are in unit of nano-meter. A typically used WL for visible light range is np.arange(360, 831, 1).

FW: function of wavelength. For a single function, it is represented as a 1D ndarray of length N. For multiple functions, they are represented as a 2D ndarray of shape (K, N), where K is the number of loaded functions, and fw[k] is the k-th function, with 0 <= k < K.