XYZ = SRGBPrimaryToXYZ(rgb)
Convert between sRGB primaries and CIE XYZ.
The rgb are linear device coordinates for the primaries of the sRGB
standard. One would expect these to be in the range 0-1, although
any scaling will simply propogate through to the XYZ coordinates.
5/1/04 dhb Wrote it.
7/8/10 dhb To ensure consistency, get matrix from XYZToSRGBPrimary rather than hard coded here.