MATLAB: How to compute min for image with black border

digital image processingImage Processing Toolbox

Hi, I have an image with black border in 2000 * 2000.after using min function the output is 0 or 1.that The minimum is related to border of the image that is black.how to compute min or max other than black border? my code is here.by this code output min is NaN.
    img=imread('image.tif');
    figure(1),imshow(img),title('original');
    [M,N]=size(img);
     for i=1:M
     for j=1:N
     if  img(i,j)<1
     img(i,j)=NaN;
    end
    end
    end     
    minofimg=min(min(img));

Best Answer

What about
min(img(img~=0))
That is, the minimum value of img values that are not zero.
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