Re: TOTALLY OFF TOPIC: 24-bit-per-pixel limit to Gdk RGB ?
- From: TORRI Vincent <Vincent Torri math u-bordeaux fr>
- To: individual <individual mi cl>
- Cc: gtk-app-devel-list gnome org
- Subject: Re: TOTALLY OFF TOPIC: 24-bit-per-pixel limit to Gdk RGB ?
- Date: Wed, 19 Feb 2003 23:02:24 +0100 (CET)
On Wed, 19 Feb 2003, individual wrote:
On Wednesday, February 19, 2003, at 12:06 PM, TORRI Vincent wrote:
http://www.yorku.ca/eye/machband.htm
One thing about this link : the fact presented at this link looks like
the
Gibbs phenomenum in the Fourier analysis. Quite interesting, as we can
consider that the eye make a Fourier transform, according to some
papers
(the eye detects the wavelength (or the frequencies, as you want) of
the
colors)
I seriously doubt it. The Gibbs "overshoot" appears in the frequency
domain, not in the spatial domain, which the lower graph represents.
Well ? I don't think so : if you take one 1-periodic funtion which is NOT
continuous (called f), f(k) its kth Fourier coefficient and Fn(x) the sum
over k=-n to n, of f(k)exp(2iPikx), and if you display Fn, you will see
the Gibbs phenomenum (L infty norm of f < a constant < L infty norm of
Fn).
Take f(x)=0 for x in [0;0.5[ and f(x)=1 for x=0.5;1] (which is almost
the function drawn in the page below) and draw Fn (n=50 for example). I
will look (a bit of course) like that.If you take f as the black function,
and do the same computations, you draw Fn and you remark that Fn goes
upper and lower than f (even if there is no Gibbs phenomenum in this
case).
The Gibbs phenomenum appears in the "spatial" domain.
My previous post was just a remark : the red curve let me think about
the gibbs phenomenum. I don't know any link between Gibbs phenomenum and
the mach bands.
regards
Vincent TORRI
Paul
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TORRI Vincent
Mathematiques Appliquees Bordeaux
Institut de Mathematiques
Universite Bordeaux 1
351 cours de la liberation
33 405 Talence cedex - France
Tel : 33 (0)5 57 96 21 42
Fax : 33 (0)5 56 84 26 26
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