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Message-ID:  <000001c36bae$79bff290$0a02a8c0@inspiron8100>
Date:         Tue, 26 Aug 2003 10:45:54 +0200
Reply-To:     [log in to unmask]
Sender:       ImageJ Interest Group <[log in to unmask]>
From:         Nick Linnenbrügger <[log in to unmask]>
Subject:      Re: manipulating real and imaginary parts of FFT?

Dear Bill,

you don't need to do the transformation twice if you're interested in
several components of the transform. When the window with the buttons for
showing real part, imaginary part, frequency spectrum etc. shows up, you can
bush several buttons one after the other to obtain various components. You
can also choose where the origin of the Fourier domain shall be placed in
each of the result images.

Anyway, if you can build your own solution, it's even better because FFTJ is
relative slow and requires lots of memory.

Best wishes,

Nick.

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> -----Original Message-----
> From: Bill Christens-Barry [mailto:[log in to unmask]]
> Sent: Monday, August 25, 2003 3:42 PM
> Subject: Re: manipulating real and imaginary parts of FFT?
>
>
> >Date:    Sun, 24 Aug 2003 14:27:31 +0200
> >From:    =?iso-8859-1?Q?Nick_Linnenbr=FCgger?= <[log in to unmask]>
> >Subject: Re: manipulating real and imaginary parts of FFT?
> >
> >Try using the FFTJ plugin, which allows the extraction of real and
> >imaginary parts of the result of a transformation. Also, you can
> >specify real and imaginary parts of the input for a transformation.
> >
> >Regards, Nick.
>
> Nick,
>
> FFTJ is great, and allows me to do these operations now. But
> doing correlation/convolution this way involves a lot of
> intermediate steps. For example, to be able to get at both
> the amplitude and phase components of the transform of an
> image, I need to transform it
> twice: once while designating that the real part be
> displayed, and once while designating that the imaginary part
> be displayed. This seems to be the only way I can access each
> part in the later multiplication I need to do.
>
> I guess I need to learn how to implement a complex processor
> reference type and implement some methods for the operations
> I'd like to facilitate. Wayne has added macro language
> commands to version 1.31e that implement correlation and
> convolution, and I'm eager to explore these.
>
> Bill
>

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