Re: [Numpy-discussion] second 2d fft gives the same result as fft+ifft

2009-06-10 Thread Béla MIHALIK
th > > Subject: Re: [Numpy-discussion] second 2d fft gives the same result as > fft+ifft > > To: "Discussion of Numerical Python" > > Date: Tuesday, June 9, 2009, 11:01 AM > > > > --- On Tue, 6/9/09, Matthieu Brucher > > wrote: > > > > &

Re: [Numpy-discussion] second 2d fft gives the same result as fft+ifft

2009-06-09 Thread David Goldsmith
Sorry, I meant: Im(iFT(FT(f))) = Im(FT^2(f)), Re(iFT(FT(f))) != Re(FT^2(f)) DG --- On Tue, 6/9/09, David Goldsmith wrote: > From: David Goldsmith > Subject: Re: [Numpy-discussion] second 2d fft gives the same result as > fft+ifft > To: "Discussion of Numerica

Re: [Numpy-discussion] second 2d fft gives the same result as fft+ifft

2009-06-09 Thread David Goldsmith
--- On Tue, 6/9/09, Matthieu Brucher wrote: > Hi, > > Is it really ? > You only show the imaginary part of the FFT, so you can't > be sure of > what you are saying. Indeed, is there not a "label" for a function f which satisfies Im(iFFT(f)) = Im(FFT^2(f)), Re(iFFT(f)) != Re(FFT^2(f))?

Re: [Numpy-discussion] second 2d fft gives the same result as fft+ifft

2009-06-09 Thread Matthieu Brucher
Hi, Is it really ? You only show the imaginary part of the FFT, so you can't be sure of what you are saying. Don't forget that the only difference between FFT and iFFT is (besides of teh scaling factor) a minus sign in the exponent. Matthieu 2009/6/9 bela : > > I tried to calculate the second fo

[Numpy-discussion] second 2d fft gives the same result as fft+ifft

2009-06-09 Thread bela
I tried to calculate the second fourier transformation of an image with the following code below: --- import pylab import numpy ### Create a simple image fx = numpy.zeros( 128**2 ).reshape(128,128).astype( numpy.float ) for i in xrang