CIELUV Transformations

[Isaac Gerg]

Feature request here.

Could CIELUV transformation be added?  CIELAB was developed for reflective media while CIELUV is for light emitting sources like monitors.  Seems that CIELUV would be a more appropriate perceptually uniform colorspace to support.

Thanks in advance,

Isaac

[Stéfan van der Walt]

Hi Isaac

On Fri, Oct 11, 2013 at 4:24 PM, Isaac Gerg <isaac...@gergltd.com> wrote:
> Could CIELUV transformation be added? CIELAB was developed for reflective
> media while CIELUV is for light emitting sources like monitors. Seems that
> CIELUV would be a more appropriate perceptually uniform colorspace to
> support.

Would you like to have a go at adding it? It can probably done by
simply adding the weights--we have all the tools in place already.
We'll also help with the pull request, as necessary.

Regards
Stéfan

[Isaac Gerg]

I am limited on time but am happy to provide code if someone can put it into github for me.

[Stéfan van der Walt]

On Fri, Oct 11, 2013 at 5:38 PM, Isaac Gerg <isaac...@gergltd.com> wrote:
> I am limited on time but am happy to provide code if someone can put it into
> github for me.

Sure, a patch is just fine.

Thanks!
Stéfan

[Isaac Gerg]

I have completed the changes to colorconv.py so that luv is now supported.  Whom do I email the file to so that it can be included in the repo?

Isaac

[Isaac Gerg]

I don't want to propagate false information and must correct myself from my initial post on this thread.

According to "Principles of Color Technology" by Roy S. Berns, it is a myth that" CIELAB was recommended for large color differences and tha tCIELUV was recommended for small color differences."  It is also a myth that "CIELAB is recommended for reflecting samples while CIELUV is recommended for sources and displays."  The second myth is what I originally stated as fact but is incorrect. 

In my literature review, several sources state these two myths are truths but provide no citations

Isaac

[Matthew Trentacoste]

I saw the initial email and was working on an implementation myself, and wrote all the test cases.  If you want to send it to me, I can integrate it with mine and make sure it passes all the tests.

[Stéfan van der Walt]

On Wed, Oct 16, 2013 at 11:29 PM, Isaac Gerg <isaac...@gergltd.com> wrote:
> According to "Principles of Color Technology" by Roy S. Berns, it is a myth
> that" CIELAB was recommended for large color differences and tha tCIELUV was
> recommended for small color differences." It is also a myth that "CIELAB is
> recommended for reflecting samples while CIELUV is recommended for sources
> and displays." The second myth is what I originally stated as fact but is
> incorrect.

This makes for good docstrings!

Stéfan

[Isaac Gerg]

I am seeing some chatter on github about the differences between CIELUV and CIELAB.  My understanding is that the committee could not agree on a single standard and didnt feel they could approve CIELAB alone.

Isaac

[Stéfan van der Walt]

On Wed, Oct 23, 2013 at 2:14 PM, Isaac Gerg <isaac...@gergltd.com> wrote:
> I am seeing some chatter on github about the differences between CIELUV and
> CIELAB. My understanding is that the committee could not agree on a single
> standard and didnt feel they could approve CIELAB alone.

Did they provide some motivation as to why not, or why both standards
are needed?

Stéfan

[Isaac Gerg]

As I understand it, they simply could not agree on a single standard and felt both must be approved.  That is as much as i can get out of the literature.

Stéfan

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[Stéfan van der Walt]

On Wed, Oct 23, 2013 at 3:25 PM, Isaac Gerg <isaac...@gergltd.com> wrote:
> As I understand it, they simply could not agree on a single standard and
> felt both must be approved. That is as much as i can get out of the
> literature.

But were arguments made on both sides that were so compelling, or did
they have different trade-offs? I'm just trying to get a grip on the
situation.

Stéfan

[Isaac Gerg]

Unfortunately, I do not know.  You could check out Principles of Color Technology by Berns and see if he talks more about it in his book.  Additionally, you could email burns and ask him.  I dont have the time at the moment to track this down.

Isaac

[Jaime Fernández del Río]

I have a coworker that is a member of one of CIE's divisions, so I asked him the LAB vs LUV question, and here's his reply:

"Yes, there is a simple historical explanation - LUV was championed by the display industry while LAB was the favorite of "surface" industries (print, materials manufacturing, ...). LUV has the beneficial property of having a saturation predictor and of being related to the luminance-linear u'v' chromaticity space. Let me know if you'd like more detail.

Today, I am not aware of LUV being used anywhere - LAB has won the battle between the two and is used even for displays. Either that, or, where higher performance is needed in terms of perceptual prediction accuracy, CIECAM02 (a color appearance model) is used. It is significantly more complex, but predicts more visual phenomena and allows for taking viewing conditions better into account.

So, I'd say use LAB if what it does is good enough and CIECAM02 if it fails (e.g., for gamut mapping LAB has serious hue non-uniformity)."

So, who's up for coding CIECAM02 color transformations, whatever that may be? ;-)

Jaime

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[Isaac Gerg]

Good stuff -- thank you for sharing.

--

[Stéfan van der Walt]

On Wed, Oct 23, 2013 at 5:56 PM, Jaime Fernández del Río
<jaime...@gmail.com> wrote:
> So, who's up for coding CIECAM02 color transformations, whatever that may
> be? ;-)

Let's see. We need someone who understands the intricacies of color
spaces. Now who could that be?

Thank you in advance!

Stéfan