On Wed, 2008-10-29 at 23:52 +0100, Joern P. Meier wrote:

> I don't think the performance is the biggest issue. However, the results
> of current (i.e. Gimp 2.6.x) downscaling are.
> In Gimp 2.4 I could use the "Cubic" Option which resulted in a little
> blurring, but that could be fixed with a judicious use of the "Sharpen"
> filter. So in the end, it yielded a lot of control about the final result.

GIMP 2.4 did not implement a "Cubic" option for downscaling. You
effectively used "Linear".

> The new Gimp 2.6 "Cubic" option usually yields too bad quality to be
> considered (I won't even begin with "Linear"). 

I guess you are running into bug #556248 here (which will be 'fixed' in
2.6.2). The result of that bug is that scaling down by a factor of 0.5
results in no interpolation at all. Even with that fixed, I would still
like to see an improvement for the downscaling algorithm in 2.6. If we
could have a proper decimation algorithm to replace the current code, I
would even consider applying that for a 2.6 release.

Hopefully we can switch to GEGL at some point for scaling. As far as I
can see there is now a promising upscaling implementation available


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