section of routines in cie.i

functions in cie.i -

 
 
 
cie_a


             cie_a(lambda)  
 
    Return CIE A illuminant (incandescent lighting) as a function of  
    wavelength LAMBDA in nm.  (2856 K Plankian)  
SEE ALSO: cie_d  
 
 
 
cie_d


             cie_d(lambda)  
         or cie_d(lambda, T)  
         or cie_d(lambda, xD, yD)  
         or cie_d(lambda, xyD)  
 
    Return CIE D illuminant (daylight) as a function of wavelength LAMBDA  
    in nm.  In the first form, return the D65 illuminant (noon daylight).  
    In the second form, T is the temperature in K (roughly 6500 for D65).  
    In the third and fourth forms, (xD,yD) or xyD=[xD,yD] are chromaticity  
    coordinates (roughly [0.31271,0.32902] for D65).  
    
    This function implements the formulas given in  
      http://en.wikipedia.org/wiki/Standard_illuminant  
    combined with the exact CIE tabulated S0,S1,S2 daylight components.  
    The CIE tabulated D65 illuminant (from http://files.cie.co.at/204.xls  
    the same source as the daylight components) differs slightly.  In its  
    single argument form, cie_d returns the best fit to the D65 table  
    from CIE, which corresponds to T=6502.849 K.  The maximum disagreement  
    with the table is less than 0.00081, while the table itself shows  
    the 0.0001 digit.  
SEE ALSO: cie_a  
 
 
 
cie_rgb


             xyz = cie_xyz(lambda)  
 
    Return the 1931 CIE RGB color matching functions at wavelength  
    LAMBDA (nm).  LAMBDA may be an array; the return value has an  
    additional trailing dimension of length 3, corresponding to  
    the [R, G, B] color matching functions.  The [R,G,B] values are  
    the (scaled) brightnesses of monochromatic primaries of wavelengths  
    700 nm (R), 546.1 nm (G), and 435.8 nm (B) (convenient to produce  
    in 1931, otherwise arbitrary), required to exactly match a fourth  
    monochromatic color of wavelength LAMBDA.  The R, G, B components  
    can be negative (especially the R component), meaning that the  
    primary must be added to the LAMBDA wavelength instead of to the  
    other primaries to achieve a match.  
SEE ALSO: cie_rgb,   cie_a,   cie_d  
 
 
 
cie_xyz


             xyz = cie_xyz(lambda)  
 
    Return the 1931 CIE standard observer color matching functions at  
    wavelength LAMBDA (nm).  LAMBDA may be an array; the return value  
    has an additional trailing dimension of length 3, corresponding to  
    the [X, Y, Z] color matching functions.  If you have a spectrum  
    as a 1D array with the same length as LAMBDA, and if the spectrum  
    is negligible outside the range of LAMBDA, then the [X,Y,Z] color  
    space coordinates for that spectrum are the integral:  
      ((spectrum * cie_xyz(lambda))(zcen) * lambda(dif))(sum,)  
    
    With the xy=1 keyword, returns only the CIE [x,y] chromaticity  
    coordinates instead of the full [X,Y,Z] color space coordinates.  
    With LAMBDA=span(380,780,n), this gives you n points around the  
    curved monochromatic locus of the CIE 1931 chromaticity diagram.  
SEE ALSO: cie_rgb,   cie_a,   cie_d