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From: ImageAnalyst <imageanalyst@mailinator.com>
Newsgroups: comp.soft-sys.matlab
Subject: Re: machine vision-Color Matching
Date: Sun, 2 Mar 2008 10:53:58 -0800 (PST)
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On Feb 27, 12:56=A0pm, "John D'Errico" <woodch...@rochester.rr.com>
wrote:
> "Vihang Patil" <vihang_pa...@yahoo.com> wrote in message
>
> <fq4372$he...@fred.mathworks.com>...
>
>
>
>
>
> > "John D'Errico" <woodch...@rochester.rr.com> wrote in
> > message <fpjlk1$3h...@fred.mathworks.com>...
>
> > > Try changing the blue pixel a bit.
>
> > > [iscolor,cn] =3D fuzzycolor([60 100 220]/255,'all');cn{find
> > (iscolor)}
> > > ans =3D
> > > blue
>
> > > Still blue, no problems. Find fuzzycolor on
> > > the file exchange.
>
> >http://www.mathworks.com/matlabcentral/fileexchange/loadFil
> > e.do?
> > > objectId=3D12326&objectType=3DFILE
>
> > > HTH,
> > > John
>
> > Hello John
> > I tried your fuzzycolor, its good, but I think it requires
> > a lot of tweaking too
> > for example
> > [iscolor,cn] =3D fuzzycolor([88 110 255]/255,'all');cn{find
> > (iscolor)}
>
> > I get no color whereas it is very much blue to me, which
> > you can see from the code below.
>
> > new =3D im2uint8(ones([128 128 3]));
> > new(:,:,1) =3D 88;
> > new(:,:,2) =3D 110;
> > new(:,:,3) =3D 255;
> > figure,imshow(new);
>
> > I think I will need to add this into the fuzzycolor's
> > database. I am still working on it. Probably you can
> > through more insight on it.
>
> > Vihang
>
> Yes, I may have missed some blues when I built
> the database. As I recall, I did try to provide an
> ability to add to or change the database.
>
> A problem is that what I considered to be a blue,
> on MY monitor, may not always coincide with
> others opinion of a blue. There are several issues
> of metamerism here to deal with. If your monitor
> is set up with a higher or lower color temperature,
> then blues might change. Or suppose one of us
> is moderately color blind, perhaps protoanomalous
> (red-green) or even tritananomalous (yellow-blue).
> Even a minor amount of such an effect can influence
> how you might see colors differently from me. Since
> different people can have subtly different pigments
> in their cones, they can see colors differently even
> if not color blind at all.
>
> These issues are why I called it fuzzy color. The
> boundaries of a color name region will be both
> irregular and fuzzy. In fact, some color name
> regions may even overlap, i.e., colors near the
> boundary of two color names like yellow/green,
> might be arguably both yellow and green.
>
> For your work, a simple solution is to build/modify
> the database for your own eyes & monitor. Ask if
> you have questions. I'd have to revisit the code,
> but it was not hard to do using the buildfuzzyluts
> function that I provided. The idea is it pops up
> a series of color planes, then you encircle those
> colors which satisfy your colorname with a
> polygon in each plane.
>
> John- Hide quoted text -
>
> - Show quoted text -

-----------------
For fun, have a look at these illusions:
http://www.psy.ritsumei.ac.jp/~akitaoka/color-e.html
particularly the one called "Green and blue spirals"  It shows you
just how deceptive perceived colors can be.

Check out all the other links at his site too.
http://www.ritsumei.ac.jp/~akitaoka/index-e.html
Most of them are quite fun and colorful.
Regards,
ImageAnalyst