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LAB2XYZ

LAB2XYZ

Name


    LAB2XYZ

Purpose


    This function returns the converted tristimulus values for a
    provided CIE L*a*b* value assuming a particular illuminant,
    namely
      X = xr * Xr
      Y = yr * Yr
      Z = zr * Zr
  where
      xr = fx^3 for fx^3 > epsilon
      xr = (116 * fx - 16) / kappa for fx^3 <= epsilon
      yr = ((L + 16) / 116 ) / kappa for L > kappa * epsilon
      yr = L / kappa for L <= kappa * epsilon
      zr = fz^3 for fz^3 > epsilon
      zr = (116 * fz - 16) / kappa for fz^3 <= epsilon
      fx = (a / 500) + fy
      fy = (L + 16) / 116
      fz = fy - (b / 200)
      epsilon = 0.008856
      kappa = 903.3
  and
      Xr, Yr, Zr are the white reference for the specified illuminant

Category


    Color Science.

Calling Sequence


    Result = LAB2XYZ( Lab, ILLUMINANT=illuminant )

Inputs


    Lab
      A 3-element vector or 3xn array of CIE L*a*b* coordinates

Keyword Parameters


    ILLUMINANT
      An optional keyword to describe the illuminant that should
      be used for the CIE L*a*b* to XYZ 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 tristimulus values

Side Effects


    None

Modification History


    Written by: Carl Salvaggio
    February, 2010 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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