Plotting median of an image on image coordinates

Question

I have a gray scale image. I want to plot the median of the columns of that image on to the image axis. For doing this I need to have two things:

1. median values of the columns (which i can obtain using the Matlab's Median command) and
2. the position of median value in image coordinate.

Can anyone help me or give a hint or an idea or any function for estimating the median position?

Answer 1

This code marks all gray-scale level values in a given column equal to median value for that column:

load clown


M = median(X, 1);

figure();
imshow(uint8(X));
hold on;

for columnIdx = 1:numel(M)
    medianValue = M(columnIdx);

    % find locations of gray-scale lavel values equal to the median        
    idx = find(X(:, columnIdx) == medianValue);

    if numel(idx) > 0
        % mark all the gray-scale level values on the image
        plot(ones(1,numel(idx)) * columnIdx, idx, '.g');
    end

end

Hope it helps