On 8/9/07, Graeme Gill <[EMAIL PROTECTED]> wrote:
> Øyvind Kolås wrote:
> > This code implements a perfect box filter for this case, what needs to
> > be added on top
> > of this to be able to do good estimate (maybe even exact) box filter
> > resamplings is trilinear interpolation by doing bilinear interpolation
> > on the two closest 50% 25% 12.5% .. levels of
> > the scaled pyramid.
>
> I'd suggest having a read of Graphics Gems I, page 147,
> "Filters For Common Resampling Tasks" by Ken Turkowski.
> Box and tent filters are easy to implement, but not necessarily
> the best choices...

For downscaling (decimating) box filtering is orders of magnitude
better than the buggy erronious use of interpolation that currently is
used in GIMP. More theoretically correct
resampling methods like a Sinc filter with an infinite neighbourhood
definitly is not something one would want in the view code. I also
doubt you will see much of a difference when doing things like
generating thumbnails etc. My gut feeling is that high quality
resampling matters
a lot more for other transformations than downscaling.

/Øyvind K.
-- 
«The future is already here. It's just not very evenly distributed»
                                                 -- William Gibson
http://pippin.gimp.org/                            http://ffii.org/
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