HELP! passing variable from one callback to another callback in GUI

 % --- Executes on button press in Embedded.
  function Embedded_Callback(hObject, eventdata, handles)
  % hObject    handle to Embedded (see GCBO)
  % eventdata  reserved - to be defined in a future version of MATLAB
  % handles    structure with handles and user data (see GUIDATA)
  global msglen
  global filesize
  global jobj2
  %image_temporary= A;

jobj=jpeg_read (get(handles.imagename,'string'));

msgstr = get(handles.EmbeddedMsg,'string');
if isempty(get(handles.EmbeddedMsg,'string')) % User tried to encode nothing!
fprintf('\n\t\t No message entered, try again.\n\n')
close(gcbf)
  return

   else

msgdbl = double(msgstr);%decimal the string
display(msgdbl)
msgbin = de2bi(msgdbl,8);
% display(msgbin)
msgbincv = reshape(msgbin,18*8, 1);
% display(msgbincv )
msg = msgbincv;
% display(msg )
msglen = length(msgbincv);
display(msglen)

key = sum(100*clock);
step = 2;
jobj2 = jpeg_steg_encode(jobj,msg,key,step);
jobj2.optimize_coding = 1;    % optimize huffman tables (optional)

jpeg_write(jobj2,'output.jpg');
d=dir('output.jpg');
filesize = d.bytes;
display(filesize)

axes(handles.stego_image);
imshow('output.jpg',handles.stego_image);
setappdata(h,'name',jobj2)

fprintf('\t\t\n Your message was encoded.\n\n');

   end
  % --- Executes on button press in retrieve.
  function retrieve_Callback(hObject, eventdata, handles)
  % hObject    handle to retrieve (see GCBO)
  % eventdata  reserved - to be defined in a future version of MATLAB
  % handles    structure with handles and user data (see GUIDATA)
  % Decode the message, and verify that it matches the original message.

msg2 = jpeg_steg_decode(jobj2,key,step);

msgrbin = vec2mat(msg2,18);

msgrbin(9:end,:) = [];

msgtdbl = transpose(msgrbin);
% display(msgtdbl)
msgrdbl = bi2de(msgtdbl);
% display(msgrdbl)
msgt = transpose(msgrdbl);
% display(msgt )
msgr = strcat(msgt);
% display(msgr  )
mlen = min(length(msg),length(msg2));
capacity = 100*mlen/(8*filesize);
if isequal(msg(1:mlen),msg2(1:mlen))
  fprintf('PASSED: Message of %d bits successfully decoded', mlen);
  fprintf(' (capacity = %.2f%%)\n', capacity);
else
  bitscorrect = length(find(msg(1:mlen)==msg2(1:mlen)));
  fprintf('FAILED: %d bit(s) incorrect\n', mlen-bitscorrect);
end
set(handles.message,'string',msgr)

I have problem when i'm passing the jobj2 from the embedded callback to retrive callback? i'm using global for jobj2 and key, step and so on.

But get error of when i used global: Attempt to reference field of non-structure array.

Answer 1

[TAB]

Global variables need to be declare global in each function where it is used.

Add below declartion line in your retrieve_Callback() function also.

global jobj2;

[mohammad asasi]

thanks you helped me with global...

I used to define a variable global only one time in the first call back...and it did,nt work.

Answer 2

[Jan]

Instead of using fragile global variables, storing the data using guidata or setappdata / getappdata locally in the figure is easier to debug.

[Yvonne ting]

yes, global variable is fragile.

is it like this if i'm using setappdata/getappdata at

the retrieve button like this?

setappdata(handles.stego_image, 'output.jpg', jobj2);

msg2 = getappdata(handles.stego_image, 'output.jpg');

pls teach me. I have already type help setappdata and getappdata in command prompt window of matlab. But, i still can't get it right...... could u pls correct me? I need someone to guide me

[Sean de Wolski]

Yes that looks good, Yvonne!

More info and examples:

http://matlab.wikia.com/wiki/FAQ#How_can_I_share_data_between_callback_functions_in_my_GUI.3F

[Alexei]

Sean de Wolski, that link you provided is FANTASTIC! Thank you! Only thing is it does not take you to the subsection directly -- just to the top of the page. But I got to where I wanted to be via ctrl+f so it's all good.