Overlay a scale bar over a running movie

Hi,

I have a GUI (made with GUIDE) in which an image sequence stored as a movie container is displayed inside an axes. The displayed movie is actually made of 2 movies, an original movie concatenated with a filtered movie. I made another GUI which opens on the press of a button, allowing the user to draw a scale bar with customizable length, color and location. I use a"line" graphics object to draw the scale bar, which works very well on the current frame in the movie. Since the line is a graphics object I guess we can store it as selected and use the handles inside the while loop, but when I do this only the handle to the line object is displayed in the workspace (eg. 180.223...) and not the scale bar on the movie.

I can't figure out how to get the scale bar still visible as the movie is playing without having to define it inside the loop. I do have the handles to the line, but I can't keep it displayed over the movie. I thought of using set(handles.ScaleBar,'HandleVisibility','on') but in vain.

Here is a simplified part of the code used to display the movie. Any clue would be really appreciated. Thanks.

   while frame <= TotalTFrameNumber 

         if frame == 0 || frame == TotalTFrameNumber % Boundary conditions...
             frame = 1; % i.e first frame
         end

         hold on    
         imshow(mov(frame).cdata,'parent',gca) % Display the current 
                                                 frame in the axes.           

         %%%%This is where I would like to display the line/scale bar.

         handles.ScaleBar = line(...); % It only displays the handles in the 
                                         workspace instead of actually drawing the line

         hold off

         drawnow

         frame = frame +1;

         if MovieIsPlaying == false % Stop condition, which stops the movie running 
                                      on the press of a button.
               break;

         end

   end

Answer 1

[Image Analyst]

Did you try the movie() function instead of imshow()?

[Ben11]

Yes I did, however I could not use it with 3D image sequences which I often have to work with (actually 5D: width, height, channels, slices and frames). So imshow is a bit slower but allows for more flexibility from what I can do with it.

The problem behind my original question about overlaying a scale bar had to do with me having trouble sharing data between my two GUIs, since once I had created a scale bar it was stuck on my image and I could not change/erase it. I think I found a workaround using setappdata and getappdata:

1) When I create the scale bar in the 2nd GUI, I use setappdata to be able to access it from the 1st GUI:

handles.ScaleBar = line(...)
setappdata(handles.pushbutton_Apply,'hScaleBar',handles.ScaleBar); 
guidata(hObject, handles);

2) I play the movie in the 1st GUI and assign the line object a handle:

while ...

   imshow(mov(frame).cdata,'parent',gca)
   hScaleBar_Play = line(...)

end ...guidata(hObject, handles);

3) After playing the movie I use setappdata with the handle of the line created while the movie was playing:

   setappdata(0, 'hScaleBar_Play',hScaleBar_Play);
   ...guidata(hObject, handles);

4) When I go back in the 2nd GUI to modify or erase the scale bar, I use getappdata to retrieve the handle hScaleBar_Play and assign it to the current scale bar handle, 'handles.ScaleBar':

   handles.ScaleBar = getappdata(0,'hScaleBar_Play');
   ...guidata(hObject, handles);

It works pretty well, althought it might not be the best way to do it and I still have to use the 'line' command inside the while loop, yet it's quite fast.

Thanks for your quick reply!

[Image Analyst]

Well imshow probably wipes it away. The way around that is to write the image directly to the 'cdata' property of the axes instead of using imshow():

set(gca, 'CData', yourImage);

Try that. Hopefully doing that won't blow away the line once it's there. You should have to do it just once and it should stay there as long as you don't call imshow() or cla().

[Ben11]

ok great thanks!