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Re: octave and image processing

From: Paul Kienzle
Subject: Re: octave and image processing
Date: Wed, 25 Dec 2002 23:03:31 -0500
User-agent: Mozilla/5.0 (Windows; U; Win 9x 4.90; en-US; rv:1.2.1) Gecko/20021130

Albert F. Niessner wrote:

I do not think that the FFT can benefit from in-place operations either
since in many instances you are going from a real matrix to a complex
matrix. Hence, you always need to create a new array because of how real
and complex are defined.

Real FFT returning complex results can be done in place. In the case of FFTW the returned array is R1 R2 ... Rn I1 I2 ... In which will need to be transposed to R1 I1 R2 I2 ... Rn In, but that can be done in place as well. There is the small problem that the octave types associated with the data assume that the data still represents a real matrix rather than a complex matrix. Short of creating a new type specifically to handle transform pairs, I can't think of a way to to handle this case, but for someone transforming signals close to the size of memory, adding a
new type may be worthwhile.

Paul Kienzle

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