[Numpy-discussion] image correlations

John Hunter jdhunter at ace.bsd.uchicago.edu
Tue May 25 10:24:01 CDT 2004


>>>>> "Todd" == Todd Miller <jmiller at stsci.edu> writes:

    >> I have a series of luminance images that I want to do some
    >> correlation analyses on.  Each image is an MxN frame of a
    >> movie.  I want to compute the correlation between a given pixel
    >> i,j, and every other pixel in the image over each frame.  That
    >> is, if I assume xij is a numFrames length time series, and xkl
    >> is another numFrames length time series (the pixel intensities
    >> at two points in the image over time), I want to compute the
    
    >> corrcoeff(xij, xkl) for every kl with ij fixed.
    
    >> I know I could do this by looping over the pixels of the image,
    >> but I'm hoping for something a bit faster.

    Todd> For numarray try numarray.convolve.correlate2d and set
    Todd> fft=1.

I've looked at this and don't know if I'm missing something or if this
isn't the right function for me.  I want to correlate a given pixel
intensity with the intensity at all other pixels over a series of
images.   Is this possible with correlate2d?

JDH






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