Reading an image on an axes and manipulate it then display it on another axes

Hie guys I have this code below. I want to read an image on axes1 then extract the green channel and then display on axes 2. How can I go about it. Thank you in advance.

   % --- Executes on button press in img_load.
    function img_load_Callback(hObject, eventdata, handles)
    [filen, pathn] = uigetfile(' *.jpg;*.bmp','select an input image');
    I = imread([pathn,filen]); %loading an image
    if ndims(I) == 3 %Number of array dimensions
        I1 = rgb2gray(I); %conversion of the color image into gray image
    else
        I1 = I;
    end
    I1 = imresize(I1,.5); % resizing the size of the image to fit in the axes
    axes(handles.axes1); %instructing axes to handle the loaded image
    image(I1);
    setappdata(0,'image',I1); %
    imshow(I1) 
    title(filen);

    % --- Executes on button press in green_channel.
    function green_channel_Callback(hObject, eventdata, handles)
    I3=getappdata(0,'image');
    green = I3(:,:,2); % Green channel
    a = zeros(size(I3, 1), size(I3, 2));
    just_green = cat(3, a, green, a);
    axes(handles.axes2);
    imshow(I3)
    axes, imshow(just_green), title('Green channel')
    image(I3);

I'm getting the following errors

Index exceeds matrix dimensions.

Error in diagnosis>green_channel_Callback (line 108) green = I2(:,:,2); % Green channel

Error in gui_mainfcn (line 95) feval(varargin{:});

Error in diagnosis (line 42) gui_mainfcn(gui_State, varargin{:});

Error in @(hObject,eventdata)diagnosis('green_channel_Callback',hObject,eventdata,guidata(hObject))

Error while evaluating UIControl Callback

Answer 1

[Greg]

You're setting the grayscale image as the appdata. This doesn't have a third dimension to index into.

Replace

    setappdata(0,'image',I1); %

with

    setappdata(0,'image',I); %

[Sico]

Thanks Greg, it worked