Re: [Algorithms] RGB to XYZ conversion

[Tom P. <ga...@fa...>]

> Dan Glastonbury wrote:
>>  What matrix should I being using to convert RGB values to CIE
>> XYZ?
>
> Good question Dan, and I for one don't know the answer.

I think the problem comes down to the fact that XYZ is an absolute
color space where RGB is flexible given the settings of your display
hardware.  Therefore the same RGB values piped through different
equipment would yield different values for XYZ if sampled with
suitable equipment.

This may be less of an issue if you're using XYZ as an intermediate
format, though, since presumably you're going to start and end with
RGB, and are doing work in XYZ space to have your transforms work
more "naturally" or whatever.  If this is the case, anything that's
out there is probably sufficient for the task, as long as you can
cleanly invert the operation for all of the values you're looking to
use.  Mind, there will be colors in XYZ that won't be representable
in RGB.  At least, as I understand it...

Sorry, I don't have any citations; I was researching this some
number of years ago for some color tools that I was working on, and
basically came to the understanding that as RGB is not an "absolute"
color scale, not to mention it is very limited, I just needed to
define the space where my operations "made sense" and transform into
and out of that space.

-tom!