pxyz2luv

Synopsis

Description

pxyz2luv converts color image from the color space XYZ to the color space L*u*v (L: Luminancy, u,v : chrominancy).

Luv is very used in calculation of small colors or color differences, especially with additive colors.

    L* = 116*((Y/Yn)^(1/3)) whether Y/Yn>0.008856
    L* = 903.3*Y/Yn whether Y/Yn<=0.008856
    u* = 13*(L*)*(u'-u'n)
    v* = 13*(L*)*(v'-v'n)

where u'=4*X/(X+15*Y*+3*Z) and v'=9*Y/(X+15*Y+3*Z)
and u'n and v'n have the same definitions for u' and v' but applied to the white point reference given par the parameter primaries. So, you have:
u'n=4*Xn/(Xn+15*Yn*+3*Zn) and v'n=9*Yn/(Xn+15*Yn+3*Zn).

The output image is of float type.

Parameters

• primaries is an integer from [0..6] which defines the type of conversion:
  • 0: illuminant E
  • 1: illuminant primaries CIE-DIN
  • 2: illuminant A primaries macbeth colour chart
  • 3: illuminant A primaries CIE
  • 4: illuminant C primaries NTSC
  • 5: illuminant C primaries CIE
  • 6: illuminant D65

Inputs

• im_in: a XYZ color image.

Outputs

• im_out: a L*u*v color image.

Result

Returns SUCCESS or FAILURE.

Examples

   pxyz2luv 4 a.pan b.pan

See also

C++ prototype

Version française

Changement d'espace couleur de XYZ vers Luv.