[Algorithms] RGB to XYZ conversion

[Dan G. <dan...@gm...>]

Dear colour space experts
 What matrix should I being using to convert RGB values to CIE XYZ?
Christer Ericson (http://realtimecollisiondetection.net/blog/?p=15)
gives the following matrix:

  M = [0.497,0.339,0.164]
      [0.256,0.678,0.066]
      [0.023,0.113,0.864]

to be used in [X Y Z] = [R G B]*M and I assume this comes from Greg
Ward's paper.  Charles Poynton's ColorFAQ and wikipedia's article on
CIE 1931 give different formulations for the conversion.

Bruce Lindbloom's site
(http://www.brucelindbloom.com/index.html?Eqn_RGB_XYZ_Matrix.html)
gives more than a dozen different conversion matrices, one of which is
labelled "sRGB" and leads me to believe this should be used for images
authored to sRGB.

My question to people more knowledgeable than I: Which of the
conversions should I be using?

thanks
DanG

-- 
Dan Glastonbury, Dan dot Glastonbury at gmail dot com
`Pour encourjay lays ortras'