How to set intervals between pictures and maximum time?

I wrote a function to answer with keys ("d" or "u") to a series of pictures. how can I set a black fullscreen (2 sec) between each picture with a maximum presentation time (5 sec) for each pictures? If the subject doesn't press the key within 5 sec, the black screen should appear. I tried with tic toc but I had problems with either fullscreen or code. I am not a Matlab expert!

risultati=zeros(48,2);
figure;
hold on;
figure('units','normalized','outerposition',[0 0 1 1]);
hFig = gcf;
hAx  = gca;
set(hAx,'Unit','normalized','Position',[0 0 1 1]);
set(hFig,'menubar','none')
set(hFig,'NumberTitle','off');
for a = 1:48
  imshow(strcat(num2str(a), '.jpg'))
  tStart = tic;
  keyspressed = [];
  k = 0;
  while ~k
      k = waitforbuttonpress;
      tElapsed = toc(tStart);
      currkey = get(gcf,'currentcharacter');
      if strcmp(currkey,'d')
          risp=0;
      elseif strcmp(currkey,'u')
          risp=1;
      else
          k=0;
      end
      risultati(a,1)=risp;
      risultati(a,2)=tElapsed;
  end
end

Answer 1

[Walter Roberson]

https://www.mathworks.com/matlabcentral/fileexchange/8297-getkeywait

[Andrea Zangrandi]

Thank you but I don't know how to use it. Can you modify my code?

[Walter Roberson]

Install getkeywait . Then

entry_timeout = 5.0;   %seconds
black_time = 2.0;      %seconds

num_pic = 48;
pic_names = cellstr( num2str( (1:num_pic).', '%d.jpg') );

risultati = zeros(num_pic, 2);

hFig = figure('units','normalized','outerposition',[0 0 1 1]);

set(hFig, 'menubar', 'none')
set(hFig, 'NumberTitle', 'off');

hAx = axes('Parent', hFig,  'Unit', 'normalized', 'Position', [0 0 1 1], 'box', 'off', 'XColor', 'none', 'YColor', 'none', 'ZColor', 'none');
hold(hAx, 'on')

for a = 1 : num_pic

    cla(hAx);
    set(hAx, 'color', 'k');
    pause(black_time);

    h = imshow( pic_names{a} );
    set(hAx, 'XColor', 'none', 'YColor', 'none', 'ZColor', 'none');  %compensate for imshow turning ticks back on
    drawnow();

    remaining_time = entry_timeout;

    tStart = tic;

    need_key = true;
    while need_key
        k = getkeywait(remaining_time);
        assert(k ~= 0, 'Internal error waiting for keypress');

        tElapsed = toc(tStart);
        remaining_time = entry_timeout - tElapsed;

        if k < 0
          %user did not enter anything within timeout
          break;
        end

        if isnan(k)         %non-ASCII key, such as control
          currkey = ' ';
        else
          currkey = char(k);
        end

        [tf, idx] = ismember(currkey, 'du');
        if tf
          risp = idx - 1;
          risultati(a,1) = risp;
          risultati(a,2) = tElapsed;
          need_key = false;
        end
    end
  end

cla(hAx);

I question your choice of imshow() for displaying the image; I think image() would be better for this purpose. imshow() reconfigures too much of the axes.

I went ahead and implemented the idea that the person has 5 seconds to get a choice of either 'u' or 'd', rather than 5 seconds between keys even if the key is not one of those two.