pxyz2lab

Converts XYZ color image to Lab color image.

Synopsis

pxyz2lab primaries [-m mask] [im_in|-] [im_out|-]

Description

pxyz2lab converts color image from the color space XYZ to the color space Lab.

LAB defines 3 components:

L est la luminancy
a is red/blue chrominancy
b is yellow/blue chrominancy

The conversion uses the matrix:

   L=116*((Y/Yn)^(1/3)) if Y/Yn>0.008856
   L=903.3*Y/Yn if Y/Yn<=0.008856
   a=500*(f(X/Xn)-f(Y/Yn))
   b=200*(f(Y/Yn)-f(Z/Zn))

where
   if Y/Yn>0.008856 f(t)=t^(1/3) 
   else f(t)=7.787*t+16/116

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 Lab color image.

Result

Returns SUCCESS or FAILURE.

Examples

   pxyz2lab a.pan b.pan

C++ prototype

Errc PXYZ2LAB( const Imc2dsf &im_in, Imc2dsf &im_out );

Version française

Changement d'espace couleur de XYZ vers Lab.

Author: Olivier Lezoray