Error in reset push button in GUI

I wanted to install a reset button in gui, by using the code below. The function (select_pet_image) was able to reset, however the other function (color_segmentation) was not able to do so. Thus, I am just able to perform this GUI for one image, that's all. My code is as shown below.

function select_pet_image_Callback(hObject, eventdata, handles)
axes(handles.axes3);
path='G:\FYP2\Time Frame\';
filter='*.png';
[selectedFile, selectedPath]=uigetfile(fullfile(path, filter));
A=imread([selectedPath, selectedFile]);
[rows, columns, numberOfColorBands] = size(A);
imshow(A);
title('PET scan Image');
setappdata(handles.select_pet_image, 'Select_a_PET_image', A);

% --- Executes on button press in color_segmentation.
function color_segmentation_Callback(hObject, eventdata, handles)
axes(handles.axes3);
data=getappdata(handles.select_pet_image, 'Select_a_PET_image');
[rows, columns, numberOfColorBands] = size(data);

if numberOfColorBands > 1
    subplot(2, 2, 1);   
    imshow(data);
    title('Original Color Image');
else
    caption=sprintf('Original Indexed Image\n(converted to true color with its stored colormap)');
    title(caption);
end

%EXTRACT OUT THE COLOR BANDS FROM THE ORIGINAL IMAGE
redBand=data(:,:,1);
greenBand=data(:,:,2);

%THRESHOLD LEVELS
redThresholdLow=215;
redThresholdHigh=255;
greenThresholdLow=220;
greenThresholdHigh=255;

redMask=(redBand>=redThresholdLow) & (redBand<=redThresholdHigh);
greenMask=(greenBand>=greenThresholdLow) & (greenBand<=greenThresholdHigh);

subplot(2, 2, 2);
imshow(redMask, []);
title('Red Pixels');

subplot(2, 2, 3)
imshow(greenMask, []);
title('Green Pixels');

yellowMask = uint8(redMask & greenMask);
subplot(2, 2, 4);
imshow(yellowMask, []);
title('Yellow Pixels');

% --- Executes on button press in reset2.
function reset2_Callback(hObject, eventdata, handles)
cla(handles.axes3);

Answer 1

[Geoff Hayes]

Looking at your code, when the color_segmentation_Callback function is called, the following line is executed

 axes(handles.axes3);

which sets the current axes to axes3. Later, within this same callback, the code calls subplot four times to create four new axes. Is this what you have intended - to replace the axes3 with four new ones? Because that would explain why your reset does not clear the axes created in color_segmentation_Callback since the reset code only calls cla on axes3 and not on any of the four new axes.

You would need to save the handle to each of these four subplots, something like

 handles.hSubplot1 = subplot(2,2,1);
 % draw stuff
 handles.hSubplot2 = subplot(2,2,2);
 % draw stuff
 handles.hSubplot3 = subplot(2,2,3);
 % draw stuff
 handles.hSubplot4 = subplot(2,2,4);
 % draw stuff

 % save the updated handles structure
 guidata(hObject,handles);

Then, in the reset function, call cla on each of these

 function reset2_Callback(hObject, eventdata, handles)
 cla(handles.axes3);

 if isfield(handles,'hSubplot1')
     cla(handles.hSubplot1);
 end

 % etc.

As an aside, you may want to update your GUI so that you have four axes, three of which are hidden and only made visible when you call color_segmentation_Callback. Else you will have difficulties when showing one axes or four.

[Gee Cheng Mun]

I tried your code, but it didnt work.

function color_segmentation_Callback(hObject, eventdata, handles)
data=getappdata(handles.select_pet_image, 'Select_a_PET_image');
[rows, columns, numberOfColorBands] = size(data);

if numberOfColorBands > 1
    handles.hSubplot1=subplot(2, 2, 1);
    imshow(data);
    title('Original Color Image');

else
    caption=sprintf('Original Indexed Image\n(converted to true color with its stored colormap)');
    title(caption);
end

%EXTRACT OUT THE COLOR BANDS FROM THE ORIGINAL IMAGE
redBand=data(:,:,1);
greenBand=data(:,:,2);

%THRESHOLD LEVELS
redThresholdLow=215;
redThresholdHigh=255;
greenThresholdLow=220;
greenThresholdHigh=255;

redMask=(redBand>=redThresholdLow) & (redBand<=redThresholdHigh);
greenMask=(greenBand>=greenThresholdLow) & (greenBand<=greenThresholdHigh);

handles.hSubplot2=subplot(2, 2, 2);
imshow(redMask, []);
title('Red Pixels');

handles.hSubplot3=subplot(2, 2, 3);
imshow(greenMask, []);
title('Green Pixels');

yellowMask = uint8(redMask & greenMask);
handles.hSubplot4=subplot(2, 2, 4);
subplot(2, 2, 4);
imshow(yellowMask, []);
title('Yellow Pixels');

%save the updated handles structure
guidata(hObject, handles);

%

   --- Executes on button press in reset2.
  function reset2_Callback(hObject, eventdata, handles)
  cla(handles.axes3);

   if isfield(handles,'hSubplot1')
       cla(handles.hSubplot1);
   end

[Geoff Hayes]

Please clarify what you mean by it didn't work. Was an error thrown or did something else happen (or not happen)?

Rather than creating new plots whenever you press your button, I think that it would be better to update your GUI to have four axes with three of them being hidden. These three would be visible only when you draw on them as in the case when pressing the colour segmentation button. When you press the reset button, then the data from all axes would be cleared and the three axes would be hidden once again.

See the attached for an example.

[Gee Cheng Mun]

I understand how to use the function better now, thanks to your attachment! However, if I create new axes and kept them hidden till I run my color_seg code. Won't there be an empty space in my gui?

[Geoff Hayes]

Yes, but the alternative is dynamically creating new ones within your GUI (which is what you were doing). Aren't you concerned that the new axes may be positioned incorrectly and so conflict with other controls (i.e. your pushbuttons)?

You could always create the four axes (with three hidden) but have your first axes sized such that it fills the empty space. When the user presses the colour segmentation button, axes1 is resized to fit the space occupied by four axes. Then, when the user presses reset, the axes is full-size again.

Note the attached (rough) example. Look in the code to where we set a "small" and "large" position array for axes1.