[Image-SIG] Re: aliasing on resize or thumnail?

[Fredrik Lundh]

marc lindahl <marc@bowery.com> wrote:
> > They do blur the picture a little for me, in comparison if NEAREST. I
> > believe what is happening - by design - is that BILINEAR and BICUBIC are
> > just exactly that: they calculate each pixel color from the four pixels
> > closest to it in the original image.
>
> That's not how it's supposed to work, to be an antialising filter, is it?

it isn't an anti-aliasing filter: the BILINEAR and BICUBIC resampling
filters are intended for geometric transforms (rotations, quadrilateral
warps), not thumbnail generation.

(and the ANTIALIAS filter isn't available in 1.1.2)

you can get a better-than-nothing result by resizing multiple times
with the BILINEAR filter; untested:

    while im.size[0] > size[0] or im.size[1] > size[1]:
        im = im.resize(
            (max(size[0], im.size[0]/2), max(size[1], im.size[1]/2)),
            Image.BILINEAR
        )

</F>