image fourier transform

Discussion in 'Python' started by Johannes Ahl-mann, Feb 15, 2005.

  1. hi,

    i've been looking all around the net (google is my friend ;-) for a
    module to apply fourier transformations on images. the different ones in
    numerical python and scientific python seem all to be operating on
    sequences and therefore seem to be 1D fourier transform.

    anyone know a library/module to do 2D image FFT in a simple manner.

    or am i just too dumb to see how this is supposed to work with the 1D
    fourier transforms??

    thx,

    Johannes
    Johannes Ahl-mann, Feb 15, 2005
    #1
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  2. Johannes Ahl-mann

    Robert Kern Guest

    Johannes Ahl-mann wrote:
    > hi,
    >
    > i've been looking all around the net (google is my friend ;-) for a
    > module to apply fourier transformations on images. the different ones in
    > numerical python and scientific python seem all to be operating on
    > sequences and therefore seem to be 1D fourier transform.


    Huh? From the FFT module which comes with Numeric:

    In [1]: import FFT

    In [2]: FFT.fft2d?
    Type: function
    Base Class: <type 'function'>
    String Form: <function fft2d at 0x1444fb0>
    Namespace: Interactive
    File: /platlib/Numeric/FFT/FFT.py
    Definition: FFT.fft2d(a, s=None, axes=(-2, -1))
    Docstring:
    fft2d(a, s=None, axes=(-2,-1))

    The 2d fft of a. This is really just fftnd with different default
    behavior.


    --
    Robert Kern


    "In the fields of hell where the grass grows high
    Are the graves of dreams allowed to die."
    -- Richard Harter
    Robert Kern, Feb 15, 2005
    #2
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  3. Johannes Ahl-mann

    Tim Roberts Guest

    Johannes Ahl-mann <> wrote:
    >
    >i've been looking all around the net (google is my friend ;-) for a
    >module to apply fourier transformations on images. the different ones in
    >numerical python and scientific python seem all to be operating on
    >sequences and therefore seem to be 1D fourier transform.
    >
    >anyone know a library/module to do 2D image FFT in a simple manner.
    >
    >or am i just too dumb to see how this is supposed to work with the 1D
    >fourier transforms??


    To do a 2D FFT on a matrix X, you do 1D FFTs on all the rows, producing X',
    then you do 1D FFTs on all the columns of X'.

    So, for a 32x32 2D FFT, you'll end up doing 64 1D FFTs.
    --
    - Tim Roberts,
    Providenza & Boekelheide, Inc.
    Tim Roberts, Feb 15, 2005
    #3
  4. On Tue, 2005-02-15 at 01:18, Tim Roberts wrote:
    > Johannes Ahl-mann <> wrote:
    > >i've been looking all around the net (google is my friend ;-) for a
    > >module to apply fourier transformations on images. the different ones in
    > >numerical python and scientific python seem all to be operating on
    > >sequences and therefore seem to be 1D fourier transform.
    > >anyone know a library/module to do 2D image FFT in a simple manner.
    > >or am i just too dumb to see how this is supposed to work with the 1D
    > >fourier transforms??

    > To do a 2D FFT on a matrix X, you do 1D FFTs on all the rows, producing X',
    > then you do 1D FFTs on all the columns of X'.
    > So, for a 32x32 2D FFT, you'll end up doing 64 1D FFTs.


    FFTW: http://www.fftw.org/
    Python bindings for it: http://pylab.sourceforge.net/

    Adam DePrince
    Adam DePrince, Feb 16, 2005
    #4
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