MATLAB: Spatial correlation of 3d matrices

correlation

Hi, I'm trying to compute the similarity of two 3d images. Is there any way to get the spatial correlation of these two images? Many thanks!

Best Answer

How about

ifftn(fftn(Image1).*conj(fftn(Image2)),'symmetric')

with zero-padding if appropriate.

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MATLAB: Normxcorr2 function – spatial / frequency domain selection

Hi Sam, normxcorr2 computes an estimate of the computation time for spatial domain correlation vs. frequency domain. Whichever is the smallest wins.

You could save normxcorr2.m as a different name and then modify the code so that it always did one or the other. For example, to always use spatial domain, you can modify the xcorr2_fast function inside of normxcorr2 as follows

function cross_corr = xcorr2_fast(T,A)
T_size = size(T);
A_size = size(A);
outsize = A_size + T_size - 1;
% figure out when to use spatial domain vs. freq domain

%conv_time = time_conv2(T_size,A_size); % 1 conv2

%fft_time = 3*time_fft2(outsize); % 2 fft2 + 1 ifft2

%if (conv_time < fft_time)

    cross_corr = conv2(rot90(T,2),A);
%else

%    cross_corr = freqxcorr(T,A,outsize);
%end

To only use the Fourier transform:

function cross_corr = xcorr2_fast(T,A)
T_size = size(T);
A_size = size(A);
outsize = A_size + T_size - 1;
% figure out when to use spatial domain vs. freq domain
%conv_time = time_conv2(T_size,A_size); % 1 conv2
%fft_time = 3*time_fft2(outsize); % 2 fft2 + 1 ifft2
%if (conv_time < fft_time)
%    cross_corr = conv2(rot90(T,2),A);
%else
    cross_corr = freqxcorr(T,A,outsize);
%end

MATLAB: Is fftn() and ifftn() equivalent to a 3D Fourier Transform in this case

fftn(X) and ifftn(X) carry out a 3-D FFT or a 3-D inverse FFT if length(size(X)) is equal to 3.

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Related Solutions

MATLAB: Normxcorr2 function – spatial / frequency domain selection

MATLAB: Is fftn() and ifftn() equivalent to a 3D Fourier Transform in this case

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