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Thread: fftw problem

  1. #1
    Join Date
    Feb 2006
    Posts
    1

    Default fftw problem

    Hi,

    i have a problem using fftw for a convolution of a image and a filter. The problem is that the dimension of the image changes (according to the documentation to nx*ny*(nz/2+1)) after using rfftwnd_one_real_to_complex. if the filter is created in fourier space (not transformed) it has the dimension of nx*ny*nz. so i have the problem that i cant just multiply the filter with the image because the size reduction in the fourier transform causes a dimension missmatch.

    example:
    image in realspace 32*32*32 with fouriertransform 32*32*17
    created in fourier space: filter 32*32*32

    in matlab for example the size does not change on fourier transforms and i can simply mutliply it:
    [matlab_code]
    wedgedImage = real(ifourier(fourier(image).*fftshift(wedge(size( image), 30)));
    [/matlab_code]


    anyone knows a solution for this problem (how to implement it with fftw)?
    lordy

  2. #2
    Join Date
    Jan 2006
    Posts
    10
    Qt products
    Qt3 Qt4
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    MacOS X Windows

    Default Re: fftw problem


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