Returns the x and y chromaticity values calculated for a given spectral power distribution (power per unit area per unit wavelength) and a selected set of color matching functions. The colormatchxy function assumes that the units of wavelength for the spectral power distribution are nanometers, for example, W/(m 2 nm). The available color functions are the CIE 1931 and CIE 1964.
The x and y values are dimensionless and they are related to the X, Y, and Z values by:
$$ x=\frac{X}{X+Y+Z}, y=\frac{Y}{X+Y+Z} $$
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Syntax |
Description |
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cmxy = colormatchxy(colormatch(spec, lam, "functions")); |
Returns x, y for the spectrum spec evaluated at the wavelength values in lam (units of meters), using the selected color functions. If no functions are specified, the "CIE 1931" set is used. |
Example
This example shows how to calculate the x, y values for a given spectral power distribution.
# create a dummy spectrum
lambda = linspace(300e-9,700e-9,500); # note SI units (meters)
spectrum = exp(-(lambda-450e-9)^2/(30e-9)^2);
plot(lambda*1e9,spectrum,"wavelength(nm)","test spectrum");
?cmxy64 = colormatchxy( colormatch(spectrum,lambda,"CIE 1964") );
result:
0.14368
0.0606946
?cmxy36 = colormatchxy( colormatch(spectrum,lambda) );
result:
0.148857
0.033839
The following figure shows the plot of the test spectrum created by the example code.
Related Publications
- https://en.wikipedia.org/wiki/CIE_1931_color_space
- CIE Proceedings (1932), 1931. Cambridge: Cambridge University Press.
- CIE Proceedings (1964) Vienna Session, 1963, Vol. B, pp. 209-220 (Committee Report E-1.4.1), Bureau Central de la CIE, Paris.
See Also
List of commands , plot , colormatchfunction , colormatch , colormatchuv