[Image-SIG] downscaling by area averaging

[Douglas Bagnall]

I've added stretched versions to

http://halo.gen.nz/pil/examples.html

With javascript, clicking on the top image should cycle through the
unscaled, area averaged, anti-aliased, and nearest-neighbour-stetched
images.

> + I'm beginning to wonder if there's not an off-by-something error
>   lurking somewhere in stretch.  hmm...

In my tests, all the resize and stretch filters appear to shift the 
image down and to the right by about half an output pixel.  Assuming my 
controls images are right...


[Earlier]

 >>Interestingly, the area averaged image is generally pixel perfect with
 >>the Gimp's best resizing ("Cubic").
 >
 > that's odd.

Without looking, I think it must be adaptive, but is called cubic 
because that is an ancient photoshop keyword for "the best possible".


douglas