On Tue, Oct 11, 2005 at 01:38:43AM +0200, cedric GEMY wrote:
> Testing 2.3, i can there is new  interpolation method called Lanczos. It 
> is described as being better than cubic. Does anyboy know simply :) how 
> it works with the picture ?

Err, a quick summary (perhaps not simple) is that Cubic interpolation uses a
third order polynomial to guess at values we don't have pixel samples for.
Lanczos is from a family of interpolation schemes called windowed sinc.

The sinc function is defined as sin(x)/x (with it being 1 at x=0).  It shows
up a lot in signal processing, and can be shown to be "ideal" for
interpolation (for some definition of ideal).  Since the real world isn't
ideal, and all trigonometric functions introduce ringing in a
non-ideal world, they window the sinc function to limit how far out the
ringing can go.

The sinc interpolation schemes tend to do a visually better job of
interpolation at the cost of more processing time (but still less than a
generic spline implementation).

I'm glad they added it.  I probably won't be personally using it much, since
my requirements are elsewhere, but it is a very useful thing to have

Incidentally, I know gamasutra had an article on sinc interpolation a few
years back that should still be easy to find (I accidentally ran across it
again a few weeks ago).  Also, http://www.mathworld.com is a great resource
for general math information.


Computer Science is as much about computers as astronomy is about telescopes
        -- Edsger Wybe Dijkstra (1930-2002)

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