Re: thresholding the RGB image

In article <gmytl.544$0E.123@xxxxxxxxxxxx> Walter Roberson <roberson@xxxxxxxxxxxx> wrote:

There are some animals or insects that have more different kinds
of cones than humans do, and so process colour (especially
ultra-violet) differently than we do. And there are other
animals or insects that have only two kinds of cones. If I recall the
lay summary I was reading last year, there is evidence that
the distant ancestors of humans had had three kinds of cones and
had lost one of the kinds, but that later one of the two remaining
kinds mutated so that we now have three -- but a different set of
three than the creatures that didn't lose the third cone somewhere
along the way.

I was close but I had the details wrong; it so happens that the
current (April 2009) Scientific American has an article about
colour vision in primates. The "old world" primates have different
3-cone colour vision than the 3-cone colour vision that the
"new world" primates have, with the mutation based upon different
genetic principles.

And there was an oddity mentioned in a side-bar: apparently some
women (female humans) have 4 kinds of rods and so in theory could
see colour differently than other people do... but whether that happens
in practice has not been studied.



.

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