Hi solar,

On Fri, Aug 1, 2008 at 6:58 AM,  <[EMAIL PROTECTED]> wrote:
> On Wed, 30 Jul 2008 15:53:36 +0200, David Gowers <[EMAIL PROTECTED]> wrote:
>
>> I've finished checking, and am just sending off the results and
>> webpage to Sven now.
>> David
>
> Thanks for all the hard work on this. A very interesting comparison.
> (Perhaps too many engraving type images tho').
>
> My main interest was in lanczos results since I spent some time on this
> (initially intending to use it as a pixelisation filter rather than
> interpolation method).
>
>
>
> One of the most interesting differences between cubic (csplines) and
> lanczos3 is shown here:
> http://svenfoo.org/scaletest/33-9.html
>
> the cubic scaling shows some exagerated contrasts especially on the top of
> the head. Almost like it has some party glitter sprinkled on it. In this
> example the linear may even, atypically, be preferable to cubic.
>
> This artifact is probably a good example of the tendancy of csplines to
> overshoot near sharp changes. The orange part of the throat is also softer
> and more natural than the cubic which show fairly obvious pixelisation
> there.
>
> Aside that, many of the samples show little discernable difference though
> the predominance of etched images , which are basically binary in tone,
> would not demonstate the overshoot phenomenon.
>
> Maybe a couple of tests with block style graphics would be a useful
> addition. Simple graphics with areas of uniform colour.

I included a pixel art (image #8) for this purpose. I agree it's not
simple -- it only has areas of uniform color.
the original is found here:
http://www.pixeljoint.com/pixelart/5647.htm#; each of the two sprites
have about 22 colors each; the borders are flat and comprise an
additional 2 colors. The picture was by me, and I felt that lanczos
performed outstandingly for downscaling -- and in general, all scaling
methods did a better job of preserving the salient features of the
image than the old code. Pixel art ('block graphics'?) is a
pathological case for most scaling algorithyms, and no algorithym old
or new performed very well on upscaling image #8.

David
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