Re: Positive image interpolation

Dave Martindale wrote:

Yes, but how was the image captured? If you start with a real-world
all-positive energy map, and properly low-pass filter it before sampling
so there is no aliasing during sampling, then when you resample this
image to some other size you will not get negative values during the
reconstruction (interpolation process)

I don't see it ... lets assume 1:1 resampling and a step edge from 0 to 1 as the original signal. After applying a low pass brick wall filter we get negative values, because of the ringing at the step edge, which after sampling and 1:1 resampling are still there.

AFAICS looking at this from the perspective of the Nyquist–Shannon sampling Theorem is a red herring, as usual when dealing with image processing.

Marco
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