Can I choose point with mouse from video?

I am thinking of live video from cam as background, I want to choose point by mouse click so I can focus on this point with servo motor to put it in the center . the problem: it seems I can't use "ginput" on video, can I?, I thought maybe I could press key in realtime so I get screenshot "imshow" which I can choose point from! but I couldn't achieve this code.

Answer 1

[Chris Barnhart]

If the live video is placed into a matlab figure object - then it might be easy. This code tracks the mouse and shows the click points.

function gui_test()

    hf = figure(1)
    set(hf,'WindowButtonMotionFcn',cb_mm);
    set(hf,'WindowButtonDownFcn',@cb_fig);
    set(hf,'WindowButtonUpFcn',@cb_fig);

function cb_mm(h,e)
        %disp(e.Source)
         disp(h.CurrentPoint)

end

function cb_fig(hobj,e)
      %disp(e.Source)
      disp(hobj.CurrentPoint);
end

end

For more details see figure properties

Answer 2

[Ahmad]

This is realy amazing. Thank you Chris very much. I'll try this soon, but I should install the 2014 edition first.

[Chris Barnhart]

I just checked 2007 as follows:

h=figure(1)
inspect(h)

It also has the Window... Fcn for callback.

However, the dot notation is possibly only 2014b, use get(hobj,'CurrentPoint') instead. This runs in 2007.

function gui_test()

      function cb_mm(hobj,e)
          %disp(e.Source)
          disp(get(hobj,'CurrentPoint'));

      end

      function cb_fig(hobj,e)
          %disp(e.Source)

          disp(sprintf('click at %d %d', get(hobj,'CurrentPoint')));
      end
  hf = figure(1)
  findfigs
  set(hf,'WindowButtonMotionFcn',@cb_mm);
  set(hf,'WindowButtonDownFcn',@cb_fig);
  set(hf,'WindowButtonUpFcn',@cb_fig);

end

Answer 3

[Ahmad]

this is very simple way to preview live video into figure:

vid = videoinput('winvideo');

figure('Toolbar','none',...
       'Menubar', 'none',...
       'NumberTitle','Off',...
       'Name','My Preview Window');

vidRes = get(vid, 'VideoResolution');
nBands = get(vid, 'NumberOfBands');
hImage = image( zeros(vidRes(2), vidRes(1), nBands) );

% Display the video data in your GUI.

preview(vid, hImage);

but I couldn't merge the WindowButtonDownFcn with it, I tried different ways but it keeps giving me mistakes, sorry but I am new to matlab, if you can help me please?