clipka <ano### [at] anonymousorg> wrote:
> Am 17.03.2011 03:49, schrieb Trevor G Quayle:
>
> > The interpolate 2 seems to cause banding at the transition points.
>
> Cubic interpolation produces "overshoot" and "undershoot" at sharp
> transitions. I usually store values from 0.25 to 0.75 in df3 files to
> avoid such problems.

I guess this is partly the wrap-around banding.  I have tried a few fixes, but
none are satisfactory.  Probably just best to not use interpolate 2 for my
current usage and stick with linear or perahps my own function coded
interpolation.

>
> > One thing I noticed is that with interpolate 1 there is a distinct shift down
> > and to the left.  Is there a bias in the internal interpolate function?  This is
> > something that I have noticed before with interpolate.
>
> It was known (and fixed) for interpolation of input images, but has
> never been examined for df3 files yet.


I ran a test with a 1/2 pixel shift which corrected it, so it does look like
this just needs to be corrected for df3 files in the code.


-tgq

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