Which image is not like the others?

I have four RGB images I1, I2, I3, and I4. 3 of them are exactly the same, and one is different. Is there an elegant solution to find which image is different? Currently, I'm using something like the following.

    if ~isequal(I1, I2) & ~isequal(I1, I3) & ~isequal(I1, I4)
        dif = I1
    elseif ~isequal(I2, I1) & ~isequal(I2, I3) & ~isequal(I2, I4)
        dif = I2
    %etc.
    end

Answer 1

[Abhishek Gangwar]

Compute difference of two images using "imabsdiff()" function, output of this function would be a matrix if both images are same, resulting matrix would have all zeros, you can use this logic.

for example:-

diff1 = imabsdiff(I1, I2);

diff2 = imabsdiff(I2, I3);

diff3 = imabsdiff(I3, I4);

diff4 = imabsdiff(I4, I1);

if sum(sum(diff1)) == 0 && sum(sum(diff2)) == 0 && sum(sum(diff3)) ~= 0 && sum(sum(diff4)) ~= 0

diff = I4;

elseif sum(sum(diff1)) == 0 && sum(sum(diff2)) ~= 0 && sum(sum(diff3)) ~= 0 && sum(sum(diff4)) == 0

diff = I3;

elseif sum(sum(diff1)) ~= 0 && sum(sum(diff2)) ~= 0 && sum(sum(diff3)) == 0 && sum(sum(diff4)) == 0

diff = I2;

elseif sum(sum(diff1)) ~= 0 && sum(sum(diff2)) == 0 && sum(sum(diff3)) == 0 && sum(sum(diff4)) ~= 0

diff = I1;

end

[Image Analyst]

diff is a built in function so you should use a different name for your output variable.

Answer 2

[KSSV]

n = numel(I1) ; 
if nnz(I1==I2==I3) == n
    dif = I4 ; 
elseif nnz(I2==I3==I4) == n
    dif = I1 ;
elseif nnz(I3==I4==I1) == n
    dif = I2 ; 
else
    dif = I3 ;
end