CODEWITHSUNDEEP
performancematlabimage-processing
Adam
Adam

Reputation: 10036

Comparing multiple images in matlab

I'm trying to do a pixel-by-pixel comparison of 20 png images stored in a cell array. For each pixel position (i,j) I want to find the pixel with the largest and smallest value from amongst the 20 images.

My current implementation seems to work, but as it's just a bunch of nested for loops it takes several minutes to finish executing. I'm looking for a more efficient method, does anyone have a suggestion? My current code is below.

min = 256;
max = -1;

for j = 1: xMax
    for k = 1: yMax
        for p = 1: 20
            if imageArray{p}(j,k) > max
                max = imageArray{p}(j,k);
            end
            if imageArray{p}(j,k) < min
                min = imageArray{p}(j,k);
            end
        end
        minImg(j,k) = min;
        maxImg(j,k) = max;
        min = 256;
        max = -1;
    end
end

Upvotes: 0

Views: 326

Answers (1)

Divakar
Divakar

Reputation: 221614

Assuming the sizes of all those images to be the same, here's one efficient approach -

%// Get dimensions of each image
[nrows,ncols] = size(imageArray{1}) 

%// Convert the cell array to a 3D numeric array for vectorized operations
im = reshape(cell2mat(imageArray),nrows,ncols,[])

%// Use MATLAB builtins min and max along the third dimension for final output
minImg = min(im,[],3)
maxImg = max(im,[],3)

Upvotes: 2

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