dr.fresch03 asked . 2020-03-16

How to use slider for image processing?

I'm working to create a tool that would measure diameter of our fibers. We've decided to create a GUI for ease of use and to change parameters when needed.

I'm creating GUI with the help of GUIDE. I want to have image updated on the axes when slider is moved, but it doesn't seem to work. Disp line is executed when slider is moved, but I'm not sure why picture isn't displayed. How do I know if bwopen line is executed? Why do variable disappear from matlab workspace? Lastly, Am I using right technique to import and handle images?

I'm totally new to this. I'm referring books to learn about GUI. I'm struggling with slider for about two weeks.

I'm referring to this text: "Learning to Program with MATLAB - Building GUI Tools"

 % --- Executes on button press in load_file.
          function load_file_Callback(hObject, eventdata, handles)
          % hObject    handle to load_file (see GCBO)
          % eventdata  reserved - to be defined in a future version of MATLAB
          % handles    structure with handles and user data (see GUIDATA)
          global read_image
          [filename, user_canceled] = imgetfile(); 
          %fmt = 'jpg';
          %[path,user_cance]=imgetfile();
          if user_canceled
              msgbox(sprintf('Error'),'Error','Error');
              return
          end
          read_image = imread(filename);
          axes(handles.axes1);
          imshow(read_image);
        % --- Executes on button press in binarize.
        function binarize_Callback(hObject, eventdata, handles)
        % hObject    handle to binarize (see GCBO)
        % eventdata  reserved - to be defined in a future version of MATLAB
        % handles    structure with handles and user data (see GUIDATA)
        global read_image
        colour_to_gray = rgb2gray(read_image);
        % Apply median filtering on grayscale image for smoothing 
        filtered_image = medfilt2(colour_to_gray); 
        %imtool(filtered_image)
        % Convert grayscale into Binary using Otsu Method 
        level = graythresh(filtered_image);
        binary = im2bw(filtered_image, level);
         axes(handles.axes1);
         imshow(binary);
        % --- Executes on slider movement.
        function xSlider_Callback(hObject, eventdata, handles)
        % hObject    handle to xSlider (see GCBO)
        % eventdata  reserved - to be defined in a future version of MATLAB
        % handles    structure with handles and user data (see GUIDATA)
        % Hints: get(hObject,'Value') returns position of slider
        %        get(hObject,'Min') and get(hObject,'Max') to determine range of slider
        global binary
        x=get(handles.xSlider, 'Value');
        xs=num2str(x);
        set(handles.xText, 'String', xs);
        disp( ' Go, go, go, world! ' ); 
        bw_open = imopen(binary, strel('disk', x)); 
        axes(handles.axes1);
        imshow(bw_open)

image processing