Undefined function or variable 'I'

I declared variable 'I' in first function(Open file GUI), like this

function Untitled_4_Callback(hObject, eventdata, handles)
[filename, pathname] = uigetfile( ...
{'*.jpg;*.gif;*.bmp*.png;*.tif',...
 'Pic File (*.jpg,*.gif,*.bmp,*.png,*.tif)';}, ...
   'Take pic!');

handles.fullImageFileName = fullfile(pathname, filename);
im_original=imread(handles.fullImageFileName );

I = imread(handles.fullImageFileName);

axes(handles.axes1);
image(im_original);

then i call 'I' in other function :

function uipushtool1_ClickedCallback(hObject, eventdata, handles)

gray = rgb2gray(I);
...etc

and error :

??? Undefined function or variable 'I'.

Error in ==> scoreRead5 at 4
gray = rgb2gray(I);

i have tried to make 'I' as global, but error too. Help me please, Masters

Answer 1

[Adam]

http://uk.mathworks.com/help/matlab/creating_guis/share-data-among-callbacks.html