[R] plotting CIE chromaticity diagram?

[Ken Knoblauch]

Unfortunately, a bad idea that looks good never dies.

That said, I still think that it is an interesting challenge
to create this graph by programming.  I can imagine that if
you specified the coordinates at a certain number of points
in the interior and along the spectrum locus, you could use
an interpolation algorithm, to reproduce what is on the
wikipedia page.  Of course, I'm kicking myself for encouraging
this be done given the opportunity it provides for misguidance
and misrepresentation.

Ken


Quoting Bryan Hanson <hanson at depauw.edu>:

> I am, unfortunately, well-aware of the limitations that Ken points   
> out (and I do appreciate him making these points).  One can readily   
> demonstrate the gamut limitations by printing the diagram Ishida   
> links to on different devices.  My hope is to get something close   
> and include a disclaimer.  Bryan
>
> On Mar 18, 2013, at 7:08 AM, Ken Knoblauch <ken.knoblauch at inserm.fr> wrote:
>
>> ishi soichi <soichi777 <at> gmail.com> writes:
>>
>>> Has anyone plotted or is it possible to plot
>>>
>>> CIE *xy* chromaticity diagram
>>>
>>> http://en.wikipedia.org/wiki/File:CIE1931xy_blank.svg
>>>
>>> I need this plot in color.
>>>
>>> ishida
>>
>> <sermon>
>> And following up on my previous mail (diatribe), after
>> having contemplated the image at the link that you
>> provide, there is another significant distortion to take
>> into account in the representation that you propose.
>> Suppose that you are considering the appearance of
>> isolated, centrally viewed lights in isolation, in neutral
>> adaptation by an observer whose vision corresponds to
>> the average observer of CIE1931.  Then, the set of primaries
>> that you will be using to generate those colors (on a screen
>> or on paper) will have a gamut that excludes a significant
>> portion of the diagram, so that if you take this limited gamut
>> and stretch it out to fill the diagram, then the coordinates of
>> the colors indicated will deviate significantly from the positions
>> in which they are represented (not to even speak of their
>> appearance).  So, in general, while this leads to a pretty
>> diagram, there is a lot of potential for misunderstanding
>> in such a (mis)representation.  </sermon>
>>
>> --
>> Kenneth Knoblauch
>> Inserm U846
>> Stem-cell and Brain Research Institute
>> Department of Integrative Neurosciences
>> 18 avenue du Doyen Lépine
>> 69500 Bron
>> France
>> tel: +33 (0)4 72 91 34 77
>> fax: +33 (0)4 72 91 34 61
>> portable: +33 (0)6 84 10 64 10
>> http://www.sbri.fr/members/kenneth-knoblauch.html
>>
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>> and provide commented, minimal, self-contained, reproducible code.
>
>



-- 
Kenneth Knoblauch
Inserm U846
Stem-cell and Brain Research Institute
Department of Integrative Neurosciences
18 avenue du Doyen Lépine
69500 Bron
France
tel: +33 (0)4 72 91 34 77
fax: +33 (0)4 72 91 34 61
portable: +33 (0)6 84 10 64 10
http://www.sbri.fr/members/kenneth-knoblauch.html