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From: Mike Horvath
Subject: CIE xyY color space
Date: 10 Mar 2017 18:19:12
Message: <58c2ee20@news.povray.org>
What value ranges are appropriate for this color space? I'm guessing Y 
(uppercase) ranges from 0 to 100. But what about x and y? Thanks.


Mike


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From: Mike Horvath
Subject: Re: CIE xyY color space
Date: 10 Mar 2017 18:21:13
Message: <58c2ee99$1@news.povray.org>
On 3/10/2017 1:19 PM, Mike Horvath wrote:
> What value ranges are appropriate for this color space? I'm guessing Y
> (uppercase) ranges from 0 to 100. But what about x and y? Thanks.
>
>
> Mike

Never mind. I just figured out they go from 0 to 1. Doh!


Mike


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From: clipka
Subject: Re: CIE xyY color space
Date: 10 Mar 2017 18:48:11
Message: <58c2f4eb@news.povray.org>
Am 10.03.2017 um 19:21 schrieb Mike Horvath:
> On 3/10/2017 1:19 PM, Mike Horvath wrote:
>> What value ranges are appropriate for this color space? I'm guessing Y
>> (uppercase) ranges from 0 to 100. But what about x and y? Thanks.
>>
>>
>> Mike
> 
> Never mind. I just figured out they go from 0 to 1. Doh!

Yup.

With the additional constraint that x+y<=1.

Y technically ranges from 0 to infinity, with no well-defined scale, and
will often be normalized so that the chosen whitepoint has Y=1 or Y=100[%].


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From: Mike Horvath
Subject: Re: CIE xyY color space
Date: 12 Mar 2017 05:04:16
Message: <58c4d6d0$1@news.povray.org>
On 3/10/2017 1:19 PM, Mike Horvath wrote:
> What value ranges are appropriate for this color space? I'm guessing Y
> (uppercase) ranges from 0 to 100. But what about x and y? Thanks.
>
>
> Mike


I tried rendering something in this color space. I've tried all the 
methods suggested so far, but am still getting "disappearing" areas of 
the shape. See the "Holes in isosurface 3" thread in p.t.s-f.


Mike


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From: Bald Eagle
Subject: Re: CIE xyY color space
Date: 15 Mar 2017 19:10:01
Message: <web.58c9911355b89017c437ac910@news.povray.org>
Mike,

With all of your experience with the various color spaces, do you think one
better lends itself to analyzing color images than the others?

For instance, see what I mean here:
http://news.povray.org/povray.binaries.images/thread/%3Cweb.5792c33271d66b005e7df57c0%40news.povray.org%3E/


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From: Mike Horvath
Subject: Re: CIE xyY color space
Date: 15 Mar 2017 23:43:50
Message: <58c9d1b6$1@news.povray.org>
On 3/15/2017 3:08 PM, Bald Eagle wrote:
> Mike,
>
> With all of your experience with the various color spaces, do you think one
> better lends itself to analyzing color images than the others?
>
> For instance, see what I mean here:
>
http://news.povray.org/povray.binaries.images/thread/%3Cweb.5792c33271d66b005e7df57c0%40news.povray.org%3E/
>
>
>
>


I'm not sure 100% what you're trying to achieve in that thread. Some 
sort of histogram of colors used in a photo?

Anyway, this shape is a personal favorite:

https://commons.wikimedia.org/wiki/File:HSL_sphere_color_solid.png


Mike


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From: clipka
Subject: Re: CIE xyY color space
Date: 16 Mar 2017 08:01:40
Message: <58ca4664$1@news.povray.org>
Am 15.03.2017 um 20:08 schrieb Bald Eagle:
> Mike,
> 
> With all of your experience with the various color spaces, do you think one
> better lends itself to analyzing color images than the others?
> 
> For instance, see what I mean here:
>
http://news.povray.org/povray.binaries.images/thread/%3Cweb.5792c33271d66b005e7df57c0%40news.povray.org%3E/

If by "analyzing" you mean anything that is related to human perception
(as opposed to anything that is related to physics), then a somewhat
perceptually uniform colour space would certainly be advantageous, such
as CIE L*a*b or CIE L*u*v, or the even newer DIN99 series of colour spaces.


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From: Bald Eagle
Subject: Re: CIE xyY color space
Date: 16 Mar 2017 12:00:00
Message: <web.58ca7dc555b89017c437ac910@news.povray.org>
clipka <ano### [at] anonymousorg> wrote:

> If by "analyzing" you mean anything that is related to human perception
> (as opposed to anything that is related to physics), then a somewhat
> perceptually uniform colour space would certainly be advantageous, such
> as CIE L*a*b or CIE L*u*v, or the even newer DIN99 series of colour spaces.

Probably true.
I recall spending much time observing your experiments with color gradients and
gamma.
(I think it would be nice to "remap" a color space from HSV to expand the very
narrow red region, and fix any other perceptually non-uniform characteristics.
Just for fun  ;) )

As for my original intent, my "analysis" is an effort to rapidly get a more
pleasing result from sampled colors for use in color maps when trying to
procedurally texture things.  You may recall my lamentations about trying to
replicate the beautiful honey-yellow coloration of a wood floor, since my color
maps only produced pale, washed-out results that weren't anywhere near what I
wanted.

A pipe-dream feature would be to have the RGB values of an area selected in the
render window (like the current re-render selected area feature) written to an
output file, which could then be used as a prototypical color mapping data set.

The edges of my brain's tentacles suggest that 3D fourier transform of that data
may well highlight the major contributing "3D" RGB vectors better than any
visualized histogram in a color space would.
Or I may just be overcomplicating the task.  ;)

I'm also wondering what algorithms various automatic pallette-generating apps
use (Android / Windows Store apps for interior decorating, selecting paint
colors, etc.)


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From: clipka
Subject: Re: CIE xyY color space
Date: 16 Mar 2017 13:40:11
Message: <58ca95bb@news.povray.org>
Am 16.03.2017 um 12:57 schrieb Bald Eagle:

> As for my original intent, my "analysis" is an effort to rapidly get a more
> pleasing result from sampled colors for use in color maps when trying to
> procedurally texture things.  You may recall my lamentations about trying to
> replicate the beautiful honey-yellow coloration of a wood floor, since my color
> maps only produced pale, washed-out results that weren't anywhere near what I
> wanted.

To be honest, no, I don't remember those lamentations.
Sounds pretty much like a gamma issue to me.


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From: Bald Eagle
Subject: Re: CIE xyY color space
Date: 16 Mar 2017 14:10:01
Message: <web.58ca9bfe55b89017c437ac910@news.povray.org>
clipka <ano### [at] anonymousorg> wrote:

> To be honest, no, I don't remember those lamentations.
> Sounds pretty much like a gamma issue to me.

It was Oct 2014, so not surprising.

http://news.povray.org/web.5435881bcbb3d8155e7df57c0%40news.povray.org


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