Matrix dimensions must agree

I tried to make a gui about LSB watermarking

% --- Executes on button press in btnChonAnhGoc2.
    function btnChonAnhGoc2_Callback(hObject, eventdata, handles)
    % hObject    handle to btnChonAnhGoc2 (see GCBO)
    % eventdata  reserved - to be defined in a future version of MATLAB
    % handles    structure with handles and user data (see GUIDATA)
    [tenAnh, duongDanAnh] = uigetfile( ...
                           {'*.jpg;*.png;*.bmp;*.jpeg;*.tif', 'All MATLAB Files (*.jpg, *.png, *.bmp, *.jpeg, *.tif)'; ...
                           '*.*', 'All Files (*.*)'}, ...
                           'Chon Hinh Anh De Mo');
    full = strcat(duongDanAnh, tenAnh);
    global anhGoc2;
    anhGoc2 = imread(full);
    anhGoc2=imresize(anhGoc2,[512,512]);
    axes(handles.axes1);
    imshow(anhGoc2);
% --- Executes on button press in btnChonWatermark2.
      function btnChonWatermark2_Callback(hObject, eventdata, handles)
    % hObject    handle to btnChonWatermark2 (see GCBO)
    % eventdata  reserved - to be defined in a future version of MATLAB
    % handles    structure with handles and user data (see GUIDATA)
    [tenAnh, duongDanAnh] = uigetfile( ...
                       {'*.jpg;*.png;*.bmp;*.jpeg;*.tif', 'All MATLAB Files (*.jpg, *.png, *.bmp, *.jpeg, *.tif)'; ...
                       '*.*', 'All Files (*.*)'}, ...
                       'Chon Hinh Anh De Mo');
    f = strcat(duongDanAnh, tenAnh);
    global anhmo;
    anhmo = imread(f);
    anhmo=imresize(anhmo,[512,512]);
    axes(handles.axes2);
    imshow(anhmo);
% --- Executes on button press in btnXuatketqua2.
function btnXuatketqua2_Callback(hObject, eventdata, handles)
% hObject    handle to btnXuatketqua2 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
global anhGoc2;
global anhmo;
k= rgb2gray(anhGoc2);
z= imbinarize(anhmo);
z= double(z);
r= double(k - mod(k,2));
l= uint8(z + r);
axes(handles.axes3);
imshow(l)

when i start the code i got Matrix dimensions must agree error at line l= uint8(z + r);

Can anyone know how to fix it?

[Stephen23]

What sizes are z and r ?

[Walter Roberson]

You resized one image to 512x512 but not the other one .

What is the purpose of testing whether ndims is not 0?

[Quan Ly Duong]

i forgot to remove it out, sorry

[Quan Ly Duong]

z size = anhmo

and r size = double(k - mod(k,2)) ??

Answer 1

[Cris LaPierre]

What version of MATLAB are you using? If pre 16b, the issue might be the 3rd dimension.

k= rgb2gray(anhGoc2); makes k a 512x512x1 matrix. As far as I can tell, anhmo remains a 512x512x3, which would cause a matrix dimension error when adding z and r in a version of MATLAB that does not support implicit expansion.

The simplest fix is probably to turn anhmo into a grayscale image as well.