XYZToLjg - aleslab/Psychtoolbox-3-aleslab-fork GitHub Wiki

Ljg = XYZToLjg(XYZ)

Convert XYZ (10 degree) to OSA Ljg coordinates. Formulae
derived from MacAdam (1974, JOSA, 64, pp. 1691-1702). Note that
MacAdam's formulae are in error for the case Y0 less than 30. The
correct formulae may be deduced by examing Semelroth's (JOSA, 1970, 16,
1685-1689) Eqn. 3, from which MacAdam's incomplete Eqn. 1 is derived.

Note that the above problem is propogated into the formulae
reported in Wyszecki and Stiles, 2cd edition. In addition, W+S
reverse the formulae for G and J and leave out the final
transformation from scriptL to L.

Finally the formualae published in Brainard (2003, Color appearance and
color difference specification. In The Science of Color, 2cd edition,
S. K. Shevell (ed.), Optical Society of America, Washington D.C., 191-216),
which correct for the above errors, introduce a new mistake: The coefficient
on B^1/3 for the j coordinate in Eq. 5-2 should be -9.7, rather than the
the +9.7 that is published.

The output of this routine was verified against the tabulated
values in W+S, Table I(6.6.4). These are republished from
MacAdam (1978, JOSA, 68, 121-130). See [OSAUCSTest](OSAUCSTest).

3/27/01 dhb Wrote it.
7/14/10 dhb Added comment that the formulae in my chapter have a typo.
The code here is and was correct.