Matlab - Imagen en un botón

a=imread('imagen.bmp');

set(handles.pushbutton2,'CData',a)

C:\Program Files\MATLAB\R2012a\toolbox\matlab\icons\tool_zoom_in.png

C:\Program Files\MATLAB\R2012a\toolbox\matlab\icons\tool_zoom_out.png

% --- Executes on button press in aumentar.

function aumentar_Callback(hObject, eventdata, handles)

zoom on

% --- Executes on button press in disminuir.

function disminuir_Callback(hObject, eventdata, handles)

zoom off

a=imread('aumentar.png');

set(handles.Boton_aumentar,'CData',a)

b=imread('disminuir.png');

set(handles.Boton_disminuir,'CData',b)

??? Error using ==> set

TrueColor CData contains element out of range 0.0 <= value <= 1.0

Error in ==> prueba>prueba_OpeningFcn at 32

set(handles.Boton_aumentar,'CData',a)

Error in ==> gui_mainfcn at 221

    feval(gui_State.gui_OpeningFcn, gui_hFigure, [], guidata(gui_hFigure),

    varargin{:});

Error in ==> prueba at 17

    gui_mainfcn(gui_State, varargin{:});

a=imread('C:\Program Files\MATLAB\R2018a\toolbox\matlab\icons\tool_zoom_in.png');

b=double(a)/(2^16);

handles.pusAbrir.CData=b;