Re: Representing Phases and Doing Calculations with them in Images?

Posted by Herbie-4 on Oct 02, 2014; 5:12pm
URL: http://imagej.273.s1.nabble.com/Representing-Phases-and-Doing-Calculations-with-them-in-Images-tp5009868p5009869.html

Dear Jacob Keller,

is it possible that you speak of the phase of Fourier-spectra not images?

Images are generally positive-valued and sometimes real-valued but never
complex-valued. If you have a complex-valued 2D signal, it shouldn't be
called an image, and I would be very much interested in how it was
generated.

"use the phases as a filter"

What does that mean? What kind of filter? What for?

Somehow clueless

Herbie

::::::::::::::::::::::::::::::::::::::::
On 02.10.14 18:46, Rebecca Keller wrote:

> Dear ImageJ Community,
>
> I've recently come across an interesting issue: representing phases an
> image. I've got phase-images with ranges -pi to +pi radians, but the trick
> is how to make this continuous range into a linear one. I.e., although the
> phases (3.13 and -3.13) are actually very close in terms of phase, they are
> far arithmetically, whereas (0.1 and -0.1) are just as close in phase but
> are very close arithmetically. I am not sure how to combine the phases,
> then, with non-cyclic information, like amplitude.
>
> My goal here is to use the phases as a filter, presumably simply by
> multiplying by the corresponding amplitudes, but for this, the closeness in
> phase to some given value should be represented by the values in the image,
> perhaps with the set value being the maximum? I guess this is equivalent to
> rotating the phases, such that the preferred value is at the "top" of the
> circle? But I can't think how to do this mathematically in the images.
>
> All the best,
>
> Jacob Keller

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