How can I find out Correlation between two image?

Question

Syed Zenith Rhyhan 2019-6-23

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/468478-how-can-i-find-out-correlation-between-two-image

编辑： Sampath Gamage 2023-3-17

采纳的回答： Image Analyst

clc;

clear all;

close all;

a=imread('1.jpg');

b=imread('2.jpg');

corr2(a,b);

____________::Error Occured::_____________

Error using corr2

Expected input number 1, A, to be two-dimensional.

Error in corr2>ParseInputs (line 35)

validateattributes(A, {'logical' 'numeric'}, {'real','2d'}, mfilename, 'A', 1);

Error in corr2 (line 21)

[a,b] = ParseInputs(varargin{:});

Error in featureExt (line 9)

corr2(a,b);

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Answer 1

Image Analyst 2019-6-23

2
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/468478-how-can-i-find-out-correlation-between-two-image#answer_380424

在 MATLAB Online 中打开

They're probably color. Do it on one color channel at a time, or use rgb2gray() to convert them to grayscale. Untested code:

grayImage1 = rgb2gray(a);
grayImage2 = rgb2gray(b);
out = corr2(grayImage1, grayImage2);

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Image Analyst 2023-3-17

在 MATLAB Online 中打开

@Sampath Gamage what do you mean by the correlation matrix? If you use corr2() that basically says how much does each pixel's value move in tandem between the two images? It's a single scalar. If you use xcorr2() you will get an image that is the sum of the two image widths and it is the cross correlation of the two images.

help corr2
 CORR2 2-D correlation coefficient.
    R = CORR2(A,B) computes the correlation coefficient between A
    and B, where A and B are matrices or vectors of the same size.
 
    Class Support
    -------------
    A and B can be numeric or logical.
    R is a scalar double.
 
    Example
    -------
    I = imread('pout.tif');
    J = medfilt2(I);
    R = corr2(I,J)
 
    See also CORRCOEF, STD2.

    Documentation for corr2
       doc corr2

    Other uses of corr2

       gpuArray/corr2
help xcorr2
 XCORR2 Two-dimensional cross-correlation.
    XCORR2(A,B) computes the crosscorrelation of matrices A and B.
    XCORR2(A) is the autocorrelation function.
 
    % Example:
    %   Find the cross-correlation of two matrices
    a = [2 1 5; 3 1 3; 5 2 2];    
    b = [1 4 3; 2 5 6];
    xcorr2(a,b)
 
    See also CONV2, XCORR and FILTER2.

    Documentation for xcorr2
       doc xcorr2