On Fri, 01 Aug 2008 13:51:02 +0200, David Gowers <00ai99@xxxxxxxxx> wrote:
> 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
yes, this is a good test for scaling alorithms. I had not really
apreciated the nature of this image since, although pixel art, it does
have predominantly degraded edges so it is not quite the sort of block
graphic I was refering to. However, picking out some specific areas, it
does give some good information on the merits of different algorithms for
this kind of image.
Viewing the comparitive for 133% at 200% (in Opera) there is a noticable
difference between cubic and lanczos.
http://svenfoo.org/scaletest/133Z8g.png
http://svenfoo.org/scaletest/133C8g.png
opening these two in adjacent tabs in opera and flipping allows direct
comparison. This difference is quite marked.
Comparing directly to the original at 266% with scaled image at 200% there
is an impressive restoration of detail lost to pixelisation in the orginal.
The eyebrow, hair and eye are well enhanced as it the hand on the blue
figure. The staircasing on the knee and thigh of the yellow figure are
also well smoothed out, though not removed completely.
All parts of this image seem to have been noticably enhanced , I think
it's a good demonstration of the lanczos code.
Although downscaling is probably the more critical test (and the case that
was needing most improvement) it may be informative to add another
enlargement to some oddball ratio (say 3.14159) to see how the detail
comes out when the result is several times bigger.
BTW , has this code been ported to the rotation operation? IIRC, that was
a separte file that closely duplicated the scaling code. Maybe this would
be a good point to unify the two.
In any case I'm very pleased to see the lanczos results on this image.
Very impressive.
regards.
--
.*.
/V\
(/ \)
( )
^^_^^
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