Re: analyzing FFT images

Posted by dpoburkoSFU on May 14, 2014; 6:40pm
URL: http://imagej.273.s1.nabble.com/Re-analyzing-FFT-images-tp5007738.html

Dear all,

   My apologies in advance if this specific question has been covered,
but I couldn't find an answer parsing the Nabble list.

   I am trying to characterize the alignment of actin filaments using
the built in FFT transform in ImageJ. We can extract some information
about when actin filaments are well organized based on the shape of the
thresholded central portion of the FFT image. But we would like to be
able to quantify the relative amounts of power over specific ranges of
frequencies in the FFT image.

  My first question is whether there is a good resource out there for
interpreting ImageJ FFT images. I understand the notion of the polar
coordinates, and I assume that the 8-bit FFT image is a saturated,
scaled version of the raw fft image, but it would be great if someone
could confirm this.

  Second, can someone enlighten me as to why the FFT images often seem
to have cross hairs along the X and Y axes?

  Third, is there a consistent formula that describe the distance in
pixels from the center of the FFT image and the corresponding frequency
encoding at that distance? I have compared the pixels/cycle shown in the
ImageJ window with the length of a line from the center of the image,
and it is fit well by a double exponential, but I don't know if that
makes sense.

  Last, is there an easy way to access the polar coordinate data in the
FFT images via macros?

Thanks,
Damon

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*Damon Poburko*, Assistant Professor | Biomedical Physiology &
Kinesiology | Simon Fraser University

Tel: [phone] | Fax: [phone] | Office L8004

Mail to: Room K9625, 8888 University Drive, Burnaby BC V5A 1S6

http://www.sfu.ca/bpk/faculty_directory/poburko.html


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