On 22/12/11 10:19, Gregor Hagedorn wrote:
Late addition, just tested VIPS with:
https://test2.wikipedia.org/wiki/Special:VipsTest?file=Fern+Groombridge.JPG&...
and found the non-bilinear VIPS version with its loss of detail rather disappointing.
Bilinear scaling with sharpen 0.8 I find unacceptable, https://test2.wikipedia.org/wiki/Special:VipsTest?file=Fern+Groombridge.JPG&...
closest results I had with 0.5: https://test2.wikipedia.org/wiki/Special:VipsTest?file=Fern+Groombridge.JPG&...
... but imagemagick is definitely still best.
To me, both of those "bilinear" scaling results look broken. At this scaling ratio, it's effectively nearest-neighbour, not bilinear. I think a loss of detail on a single-pixel level is preferable to the extreme aliasing artifacts caused by nearest-neighbour downsampling.
In this particular image, maybe you could mistake the result of nearest-neighbour interpolation for contrast enhancement. In images with more contrast in the fine detail, the breakage is unequivocal. Try today's featured picture:
Is it possible to use VIPS only for oversized images?
We'll probably only use it for TIFFs and large PNGs, not JPEGs.
-- Tim Starling