readDir.m

% Creates a list of all pictures and their exposure values in a certain directory.
%
% Note that the directory must only contain images wich are named according to the
% naming conventions, otherwise this function fails.
% 
% Filename naming conventions:
% The filename of a picture must contain two numbers specifying the
% exposure time of that picture. The first number specifies the nominator,
% the second one the denominator. E.g. "image_1_15.jpg" specifies that this
% image has been taken with an exposure of 1/15 second.
function [filenames, exposures, numExposures] = readDir(dirName)

    filelist = dir(dirName);
    for i = 3:size(filelist,1)
        filenames{i-2} = strcat(dirName,filelist(i).name);
    end

   
    i = 1; 
    for filename = filenames
        filename = filename{1};
        [s f] = regexp(filename, '(\d+)');
        nominator = filename(s(1):f(1));
        denominator = filename(s(2):f(2));
        exposure = str2num(nominator) / str2num(denominator);
        exposures(i) = exposure;
        i = i + 1;
    end

    % sort ascending by exposure
    [exposures indices] = sort(exposures);
    filenames = filenames(indices);

    % then inverse to get descending sort order
    exposures = exposures(end:-1:1);
    filenames = filenames(end:-1:1);
    
    numExposures = size(filenames,2);