You wrote:

> I don't want to say much about what type of interpolation is good
> for what and when, since I don't have the knowledge that for. But 2
> things I'd like to comment:

> 1.) No more interpolation Options?

> David Gowers mentioned: "Do we even need to offer a choice of
> algorithym for downscaling (Box filter of appropriate size should be
> ok, except for None, which should be obvious.)?"

> I can hardly imagine not to have the choice of interpolation for
> downscaling. Different interpolations give different results, and
> sometimes you want it a bit crisper, sometimes a bit softer...

> 2.) Interpolation options separately for Up- and Down-Scaling?

> Nicolas Robidoux said, that as an alternative [to a smarter
> algorithm], he could imagine separate GUI Options for Up- and
> Down-Scaling.

> I think, most user will think upon that: "It's a joke, isn't it?" ;-)

For the record:

I was being totally serious. 

The users who happen to know that there is no simple method which does
really well for both (drastic) upsampling and (drastic) downsampling
may be happy to see that different methods are used for the two
different cases.

To reiterate:

Once methods good for downsampling (like box) and upsampling (like
bicubic and lanczos) are implemented, either:

We make the choice for the users of which method is used (ideally
using two different methods something different is done in different
directions, for example, bicubic in the enlargement direction(s) and
box in the shrinking direction(s) if the user chose bicubic), which
more or less is what David suggested;


We choose defaults for them but make it visible that we use different
methods in different directions, allowing them to modify the default
choices, which is my suggestion. 

Implementation note:

If two different methods are used, do the upsampling with the "better
for enlargements" method first (unless you can do them both at once,
but this is quite challenging programming wise). This approach is
slower, but will give better results.

Gimp-developer mailing list

Reply via email to