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XYZ2LAB

XYZ2LAB

Name


    XYZ2LAB

Purpose


    This function returns the converted CIE L*a*b* values for a
    provided tristimulus value assuming a particular illuminant,
    namely
      L* = 116 * f( Y / Yw ) - 16
      a* = 500 * [f( X / Xw ) - f( Y / Yn )]
      b* = 200 * [f( Y / Yw ) - f( Z / Zn )]
    where
      f(x) = x^(1/3) for x > 0.008856
      f(x) = 7.787 * x + 16/116 for x <= 0.008856

Category


    Color Science.

Calling Sequence


    Result = XYZ2LAB( xyz, ILLUMINANT=illuminant )

Inputs


    xyz
      A 3-element vector or 3xn array of tristimulus values

Keyword Parameters


    ILLUMINANT
      An optional keyword to describe the illuminant that should
      be used for the XYZ to CIE L*a*b* conversion
          0 - D65 (Daylight) [DEFAULT]
          1 - Illuminant A (Tungsten)
          2 - Illuminant F2 (Cool White Fluorescent)
          3 - Illuminant F11 (Narrow Band Fluorescent)
          4 - Illuminant F7 (Daylight Fluorescent)
          5 - Illuminant F8 (Daylight Fluorescent)

Return Value


    Result is either a 3-element vector or a 3xn array that contains
    the computed CIE L*a*b* coordinates

Side Effects


    None

Modification History


    Written by: Carl Salvaggio
    January, 2008 Original code
    April, 2012 Corrected white reference scaling error
   

Disclaimer


    This source code is provided "as is" and without warranties as to performance
    or merchantability. The author and/or distributors of this source code may
    have made statements about this source code. Any such statements do not
    constitute warranties and shall not be relied on by the user in deciding
    whether to use this source code.
    This source code is provided without any express or implied warranties
    whatsoever. Because of the diversity of conditions and hardware under which
    this source code may be used, no warranty of fitness for a particular purpose
    is offered. The user is advised to test the source code thoroughly before
    relying on it. The user must assume the entire risk of using the source code.



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