saving image after using slider

HI, I have problem with slider.

function slidergamma_Callback(hObject, eventdata, handles)
x=get(hObject,'Value');
imga=handles.imga;
imgas=imga.^x;
axes(handles.axes4);cla;
imshow(imgas);
set(handles.edit1,'String',num2str(x));

update(handles)
%guidata(hObject,handles);

It changes the value of gamma function . The function works but I need to safe image(handles.imga) and there is a problem. When I don´t use guidata(hObject,handles) at the end of the function ,the image is not upgraded and it always save the original image , when i use guidata(hObject,handles) saving works, but slider doesn´t work very well ( it doesn´t get real value of slider but I don´t now maybe it multiply values). Do somebody knows where is the problem?

Thanks a lot

j.

Answer 1

[Image Analyst]

Try

imgas= double(imga) .^ x;
axes(handles.axes4);
cla;
imshow(imgas, []); % The [] is important!

[Image Analyst]

P.S. To save it you will have to convert to uint8 or uint16, or else save it in a .mat file.

[janepear]

Why I need to convert it to uint8? (i teried it but it doesn´t work anyway) thanks

[Image Analyst]

Usually image formats want integers. You didn't show how you were saving the files. Where is your call to imwrite()?

[janepear]

I have a pushbuton for saving.

    % --- Executes on button press in pushbuttonsave.
    function pushbuttonsave_Callback(hObject, eventdata, handles)
    % hObject    handle to pushbuttonsave (see GCBO)
    % eventdata  reserved - to be defined in a future version of MATLAB
    % handles    structure with handles and user data (see GUIDATA)
    [file path]= uiputfile('*.jpg','Ulož..');
     uloz=[path file];
      imwrite(handles.imga,uloz,'jpg');

[Image Analyst]

Did you cast imga to double before raising it to a power? It doesn't look like it. Try that.

[janepear]

 I load image and transfer im2double AND rgb2gray.

[Image Analyst]

That's the key that you left out. im2double() convert the image into the range 0-1 if the input is an integer. Most disk formats don't like floating point images in that range.

[janepear]

but if it is like you said i couldn´t save this image too, but It saved image (which is transfer to im2double) but only original, not the image which is changed by slider...In thought that the problem is somewhere in the slider.... Because I have the same operation but not as a slider but like a pushbutton and it works great and it´s the same picture ( in im2double and rgb2gray)

[Image Analyst]

Well, are you calling imwrite() once or twice? From the code you showed, it looks like you're calling it just once, so why do you think it would save both images? However that was for some button callback, not the slider callback, which you haven't shown yet.

[janepear]

ok I call once picture by imread then I save pisture to handles.imga and work with it. I don´t think it save both i think that i save the image in handles.imga ..ok I show you all code And once more i don´t have problem with saving or not working slider i have the problem, that when I use guidata(hObject,handle) the slider (i think) updates every step and save it to handle.imga so I cant´t move by slider more times because I´t not reversible operation. But if i don´t use guidata(hObject,handle) It works, I can change the value and see on the picture how gamma change this picture but i cant save it, becuase( i think) the handle.imga is not updated.

      function update(handles)
        I=handles.imga;
          imga=(I);
          handles.imga=imga;
          axes(handles.axes8);
         imhist(handles.imga);

      function pushbuttonload_Callback(hObject, eventdata, handles)
      % hObject    handle to pushbuttonload (see GCBO)
      % eventdata  reserved - to be defined in a future version of MATLAB
      % handles    structure with handles and user data (see GUIDATA)

      %%%%% NACTENI OBRAZU, JEHO INFORMACE A NASTAVENI DO AXES 1 A 2 
      [soubor cesta]=uigetfile({'*.jpg';'*.bmp';'*.jpeg';'*.png'}, 'Načti obrázek');
       filename=fullfile(cesta, soubor);
       handles.file=filename;

       [fpath, fname, fext]=fileparts(soubor);
       validex=({'.bmp','.jpg','.jpeg','.png'});
       found=0;
       for (x=1:length(validex))
       if (strcmpi(fext,validex{x}))
           found=1;
            imga = imread(filename);

            if ndims(imga) == 3
              imga = rgb2gray(imga);
            end

            imga =im2double(imga);
            handles.imga = imga;

      axes(handles.axes4); cla; imshow(handles.imga);
      axes(handles.axes5); cla; imhist(handles.imga);                                    
       guidata(hObject,handles);
      update(handles)

    % --- Executes on button press in pushbuttonsave.
    function pushbuttonsave_Callback(hObject, eventdata, handles)
    % hObject    handle to pushbuttonsave (see GCBO)
    % eventdata  reserved - to be defined in a future version of MATLAB
    % handles    structure with handles and user data (see GUIDATA)
    [soubor cesta]= uiputfile('*.jpg','Ulož..');
     uloz=[cesta soubor];

     imwrite(handles.imga,uloz,'jpg'); 
     function slidergamma_Callback(hObject, eventdata, handles)
    % hObject    handle to slidergamma (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

     set(handles.pushbuttonsave,'Visible','on');
     set(handles.pushbutton20,'Visible','off');
    x=get(hObject,'Value');
    imga=handles.imga;
    imgas=imga.^x;
    axes(handles.axes4); 
    cla;
    imshow(imgas,[]);
    set(handles.edit1,'String',num2str(x));

    handles.imga=imgas;
    update(handles)
    guidata(hObject,handles);

    % --- Executes during object creation, after setting all properties.
    function slidergamma_CreateFcn(hObject, eventdata, handles)
    % hObject    handle to slidergamma (see GCBO)
    % eventdata  reserved - to be defined in a future version of MATLAB
    % handles    empty - handles not created until after all CreateFcns called

    % Hint: slider controls usually have a light gray background.
    if isequal(get(hObject,'BackgroundColor'), get(0,'defaultUicontrolBackgroundColor'))
        set(hObject,'BackgroundColor',[.9 .9 .9]);
    end

    % --- Executes on button press in pushbuttongamma.
    function pushbuttongamma_Callback(hObject, eventdata, handles)
    % hObject    handle to pushbuttongamma (see GCBO)
    % eventdata  reserved - to be defined in a future version of MATLAB
    % handles    structure with handles and user data (see GUIDATA)

     x=handles.imga;
      gamma= x.^0.7 ;
      handles.imga=gamma;
      axes(handles.axes4);
      cla;
     imshow(handles.imga);
     update(handles);
      guidata(hObject,handles);

   So the program load picture, then is splot to axes4 and its´ histogram to axes5. If you click on pushbutton it change the image by gamma correction whit value 0.7 and if you want you can change the value yourself.