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Autocorrelation using Fourier

Posted by vischer on Dec 13, 2010; 10:19pm
URL: http://imagej.273.s1.nabble.com/Autocorrelation-using-Fourier-tp3686185.html

Hello all,

I created a test macro that performs 1D autocorrelation.
It runs well in a few seconds, but I wonder if the speed can be improved by Fourier techniques for larger data sets.

The macro first creates a test image that is randomly covered with white horizontal lines with a mean length of 20 pixels. The image is then periodically multiplied with a horizontally shifted copy, so I get the autocorrelation plot from which I can derive the mean line length. The output looks like this:

  Simulated Length = 20.17
  Measured Length = 20.06

Later in reality, the white lines will represent the fluorescent duration of molecules, and the data set will be much larger.
I doubt that a native plugin will do the same thing much faster, but has anyone a suggestion how to use Fourier techniques?

My demo macro can be downloaded from:
http://simon.bio.uva.nl/objectj/GenericMacros/AutoCorrelation/AutoCorrelation-2.txt
 

Norbert Vischer