In this Matlab GUI Tutorial, you will learn how to use radio buttons, toggle buttons and the button group panel.

Radio buttons and Toggle buttons are used exactly the same way that check boxes are used in Matlab GUIs, so we won’t go over how to use them. But there is one special case that needs to be covered. When either radio buttons or toggle buttons are used in conjunction with the button group panel, they exhibit mutually exclusive behavior. Simply put, this means that only one radio button or one toggle button can be selected at a time. This behavior can come in very useful for some GUIs. Since radio buttons and toggle buttons are identical in their functionality, what is said about one, is true for the other. Thus, only radio buttions will be discussed from here on out.

In this part of the tutorial, we will create a button group that will allow you to choose between different font sizes for the display text.

1. The first thing we need to do is to add a Button Panel component to the GUI figure that we were just working with. So if you closed GUIDE, reopen it again. Once you have GUIDE opened again, click on and add one Button Panel component to the GUI figure. Make sure it’s large enough to fit in three radio buttons. Next, click on and add three radio buttons onto the button group panel.

2. Double click on the first Radio Button component to bring up the Property Inspector. Change the String property to 8. Change the Tag property to fontsize08_radiobutton.

   

   Next, double click on the second Radio Button component, and change the String property to 12, and change the Tag property to fontsize12_radiobutton.

   Next, double click on the third Radio Button component, and change the String property to 16, and change the Tag property to fontsize16_radiobutton.

   Finally, double click on the button group panel and change the Tag property to fontSelect_buttongroup. You should also change the String property for the button group panel to Fontsize.

3. Here’s what your figure should look like after you add the components and modify them.

   

4. Before we move on, we should check the hierarchical structure of the GUI figure. Click on the icon and the followinging should appear:

   

   Make sure that the three radio buttons are one hierarchy below the button group icon.

5. Add the following line of code to the opening function. In this tutorial example, it is named button_tutorial_OpeningFcn function. Yours will be the name of the file you saved it as, followed by “_OpeningFcn”.

   set(handles.fontSelect_buttongroup,'SelectionChangeFcn',@fontSelect_buttongroup_SelectionChangeFcn);

   Make sure the previous line was added right before the line:

   guidata(hObject, handles);

   Next, add the following function at the very end of the .m file.

   function fontSelect_buttongroup_SelectionChangeFcn(hObject, eventdata)   %retrieve GUI data, i.e. the handles structure
   handles = guidata(hObject);   switch get(eventdata.NewValue,'Tag')   % Get Tag of selected object
       case 'fontsize08_radiobutton'
         %execute this code when fontsize08_radiobutton is selected
         set(handles.display_staticText,'FontSize',8);   case 'fontsize12_radiobutton'
         %execute this code when fontsize12_radiobutton is selected
         set(handles.display_staticText,'FontSize',12);   case 'fontsize16_radiobutton'
         %execute this code when fontsize16_radiobutton is selected
         set(handles.display_staticText,'FontSize',16);
       otherwise
          % Code for when there is no match.   end
   %updates the handles structure
   guidata(hObject, handles);

6. Notice that the callback functions for the radio buttons were not automatically generated by Matlab. This is completely normal. Each time a button is selected within the Button Group Panel component, the function defined within the SelectionChangeFcn property of Button Group Panel component is called. The line of code that was added in the opening function specifies the callback function when a button within the button group is selcted. The selection change function is then defined at the end of the .m file.

7. Now that we’ve completed both the visual and code aspects of the GUI, its time to run the GUI again. Try clicking on all of the buttons to make sure they perform their function correctly. Specifically, make sure that the font size changes accordingly.

   

And that’s it. Those are the basics of using the different buttons within the Matlab GUI.

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According to the official statement “Google Goggles works best on books & DVDs, landmarks, logos, contact info, artwork, businesses, products, barcodes, or text. Right now, it’s not so good at pictures of animals, plants, cars, furniture, or apparel”.

It does not surprise me that Google has developed this application. What is most interesting is how quickly Google has transformed ongoing research into a product. It was only a few months back that I read the Google paper on landmark identification, and here it is neatly bundled into an application.

My interest in Computer Vision and object recognition also makes me wonder as to how the folks at Google were able to make all this work at such a large scale. The paper I reference above provides clues but the transforming the said research into an application has some serious data flow problems. One answer can be inferred from the statement quoted above. The user has has to specify a category before with the search image. Meaning there is some case specific optimization involved. If this is true, the image search problem in the general case is still un solved!

Here are some links:

http://www.google.com/mobile/goggles/

http://www.google.com/googleblogs/pdfs/google_landmark_recognition.pdf

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You can select from a number of types; News, Face, Clip art, Line drawings and Photo. The filtered results are extremely quick and accurate. Moreover, you can also choose a color and Google would give you the images where the selected image is dominant.

Being interested in Image processing myself I know that the second is pretty easy but, categorizing the images between News, Face, Clip art, Line drawings and Photo is pretty darn difficult.

I am a little awe struck and I little worried about my FYP now

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A friend of mine posted this picture of me on Facebook. In the same days I had studied a few topics in my Digital Image Processing course on how to correct certain types of images. So I applied histogram equalization on the image followed by a butterwoth low pass filter, using Matlab code.

If anyone wants the code, please leave a comment.

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It is often an issue to handle user defined data when working with Matlab GUI. In this tutorial I show how to share user data among functions and how to handle Images.

I assume basic knowledge of Matlab GUI. (Please see the tutorial on GUI basics).

We create a simple GUI where a user can select an image and then press a button to display it.

First create a simple GUI with an edit box and two push buttons.

The plan of action is to allow the user to select a file when he/she presses the ‘Browse’ button, and show the image when he ‘Show Image’ button is pressed.

Reading Images and Setting User Data

In the ‘Browse’ button call back i add the following code.

   1: % get a file to read 

   2: [FileName, FilePath] = uigetfile({ '*.jpg'; '*.jpeg'; '*.bmp'; '*.gif'; '*.tiff'; '*.png' }, 'Select an Image...');

   3: % set the file name and path to the edit box as well

   4: set(handles.editFilePath, 'String', [FilePath, FileName]);

   5: % read the image

   6: I = imread([FilePath, FileName]);

   7: % set the image in the user data, if this is not done, the image would be

   8: % lost

   9: setappdata(JigsawPuzzle, 'MyImage', I);

  10: % set the file name and path in the user data

  11: setappdata(JigsawPuzzle, 'FileNameAndPath', [FilePath, FileName]);

The last two lines are the most important and need explanation.

setappdata(JigsawPuzzle, ‘MyImage’, I);

The first argument of the ‘setappdata’ is the name of a figure object or any object contained within it that will hold the data as its data object, you could use any control but I use the figure itself to assert the global scope of the variables. The second argument is the name of the data variable. The third argument is the data itself.

The last line sets another variable with filename and path, concatenated together.

PS: You might want to read about uigetfile (Use help uigetfile in Matlab).

I have also added similar code to the edit box.

   1: FilePath = get(handles.editFilePath, 'String');

   2: set(handles.editFilePath, 'String', FilePath);

   3: I = imread(FilePath);

   4: setappdata(JigsawPuzzle, 'MyImage', I);

   5: setappdata(JigsawPuzzle, 'FileNameAndPath', FilePath);

Retrieving User Data and Showing the image

This part is rather simpler. I add the following code to the show image button.

   1: Image = getappdata(JigsawPuzzle, 'MyImage');

   2: figure, imshow(Image);

The  getappdata is similar to get function used to retrieve values for control properties.

Please feel free to leave comments and questions.

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Here is a simple 4 step method to get you started with Matlab GUI.

I assume some background with other GUIs and Matlab.

We will create this Matlab GUI in 4 simple steps.

Step 1: Creating a Blank GUI

The Matlab GUI development tool is called GUIDE. To open this tool simply type ‘guide’ on the command window.

Select Blank GUI from the options on the left and click OK. A blank Matlab GUI (.fig file) is created.

Note: You can also set where to save this file by checking the ‘Save new figure as:’ check box.

Step 2: Creating the Interface

Creating the GUI interface is pretty simple, we have a controls toolbar from where you simply drag and drop onto your GUI.

I have added three edit boxes and a push button. The goal is to create a simple GUI based adder.

You can use the static text control to create labels for you text boxes and your GUI.

To change the color and text on the controls, use the property inspector. The two main properties that would concern us for now are ‘String’ and ‘Tag’. ‘String’ is the display text of the control where as ‘Tag’ is the handle of the control accessible from the code.

Step 3: Retrieving and Validating Data

Every control has a Callback function which is called when the control is used. First we set the Callbacks for the two edit boxes and validate data.

   1: function edit_num1_Callback(hObject, eventdata, handles)

   2: % hObject handle to edit_num1 (see GCBO)

   3: % eventdata reserved - to be defined in a future version of MATLAB

   4: % handles structure with handles and user data (see GUIDATA)

   5: % Hints: get(hObject,'String') returns contents of edit_num1 as text

   6: % str2double(get(hObject,'String')) returns contents of edit_num1 as a double

Now we wish to retrieve the data contained in edit_num1 (the first of the two edit boxes).

   1: %get the String data from the control

   2: % and check if it is empty

   3: a = str2double(get(hObject, 'String'));

   4: if (isempty(a))

   5: %     if data is empty set the data to 0

   6:     set(handles,'String' ,'0');

   7: end

   8: guidata(hObject, handles);

We add similar code for the edit_num2.

Step 4: Adding functionality

First create the call back for the push button.

In the push button call back add the following code.

   1: % get the data of both edit boxes

   2: a = str2double(get(handles.edit_num1, 'String'));

   3: b = str2double(get(handles.edit_num2, 'String'));

   4: % add the two

   5: c = a+b;

   6: % set the data into the answer edit

   7: set(handles.edit_ans, 'String', num2str(c) );

   8: guidata(hObject, handles);

Note how we get information from the edit boxes. Also note that we have to call guidata(hObject, handles); to make the updates to the edit_ans useful.

I hope you find this tutorial useful, please feel free to leave your comments and questions.

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