Berikut ini merupakan tutorial cara membuat citra berwarna menjadi lebih terang/gelap menggunakan Graphical User Interface (GUI) MATLAB. Langkah-langkahnya adalah sebagai berikut:

1. Buatlah rancangan GUI MATLAB yang terdiri dari 2 axes, 2 pushbutton, dan 1 slider seperti tampak pada gambar di bawah ini

2. Hapus xTick, yTick, dan zTick pada masing-masing axes
3. Ubahlah string pada masing-masing pushbuttton dengan nama Buka Citra, dan Exit
4. Ubahlah Min slider menjadi -255 dan Max menjadi 255
5. Listing Program-nya adalah sebagai berikut

function varargout = Terang_Gelap(varargin)
% TERANG_GELAP M-file for Terang_Gelap.fig
%      TERANG_GELAP, by itself, creates a new TERANG_GELAP or raises the existing
%      singleton*.
%
%      H = TERANG_GELAP returns the handle to a new TERANG_GELAP or the handle to
%      the existing singleton*.
%
%      TERANG_GELAP('CALLBACK',hObject,eventData,handles,...) calls the local
%      function named CALLBACK in TERANG_GELAP.M with the given input arguments.
%
%      TERANG_GELAP('Property','Value',...) creates a new TERANG_GELAP or raises the
%      existing singleton*.  Starting from the left, property value pairs are
%      applied to the GUI before Terang_Gelap_OpeningFcn gets called.  An
%      unrecognized property name or invalid value makes property application
%      stop.  All inputs are passed to Terang_Gelap_OpeningFcn via varargin.
%
%      *See GUI Options on GUIDE's Tools menu.  Choose "GUI allows only one
%      instance to run (singleton)".
%
% See also: GUIDE, GUIDATA, GUIHANDLES

% Edit the above text to modify the response to help Terang_Gelap

% Last Modified by GUIDE v2.5 01-Jan-2013 17:27:42

% Begin initialization code - DO NOT EDIT
gui_Singleton = 1;
gui_State = struct('gui_Name',       mfilename, ...
    'gui_Singleton',  gui_Singleton, ...
    'gui_OpeningFcn', @Terang_Gelap_OpeningFcn, ...
    'gui_OutputFcn',  @Terang_Gelap_OutputFcn, ...
    'gui_LayoutFcn',  [] , ...
    'gui_Callback',   []);
if nargin && ischar(varargin{1})
    gui_State.gui_Callback = str2func(varargin{1});
end

if nargout
    [varargout{1:nargout}] = gui_mainfcn(gui_State, varargin{:});
else
    gui_mainfcn(gui_State, varargin{:});
end
% End initialization code - DO NOT EDIT


% --- Executes just before Terang_Gelap is made visible.
function Terang_Gelap_OpeningFcn(hObject, eventdata, handles, varargin)
% This function has no output args, see OutputFcn.
% hObject    handle to figure
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
% varargin   command line arguments to Terang_Gelap (see VARARGIN)

% Choose default command line output for Terang_Gelap
handles.output = hObject;
movegui(hObject,'center')
% Update handles structure
guidata(hObject, handles);

% UIWAIT makes Terang_Gelap wait for user response (see UIRESUME)
% uiwait(handles.figure1);


% --- Outputs from this function are returned to the command line.
function varargout = Terang_Gelap_OutputFcn(hObject, eventdata, handles)
% varargout  cell array for returning output args (see VARARGOUT);
% hObject    handle to figure
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)

% Get default command line output from handles structure
varargout{1} = handles.output;


% --- Executes on button press in pushbutton1.
function pushbutton1_Callback(hObject, eventdata, handles)
% hObject    handle to pushbutton1 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
set(handles.slider1,'value',0);
[name_file1,name_path1] = uigetfile( ...
    {'*.bmp;*.jpg;*.tif','Files of type (*.bmp,*.jpg,*.tif)';
    '*.bmp','File Bitmap (*.bmp)';...
    '*.jpg','File jpeg (*.jpg)';
    '*.tif','File Tif (*.tif)';
    '*.*','All Files (*.*)'},...
    'Open Image');

if ~isequal(name_file1,0)
    handles.data1 = imread(fullfile(name_path1,name_file1));
    axes(handles.axes1);
    imshow(handles.data1);
    axes(handles.axes2);
    imshow(handles.data1);
    info = imfinfo(fullfile(name_path1,name_file1));
    bitdepth = info.BitDepth;
    handles.bitdepth = bitdepth;
    guidata(hObject,handles);
else
    return;
end

% --- Executes on button press in pushbutton2.
function pushbutton2_Callback(hObject, eventdata, handles)
% hObject    handle to pushbutton2 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
delete(handles.figure1);

% --- Executes on slider movement.
function slider1_Callback(hObject, eventdata, handles)
% hObject    handle to slider1 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)

% Hints: get(hObject,'Value') returns position of slider
%        get(hObject,'Min') and get(hObject,'Max') to determine range of slider
nilai_slider = get(handles.slider1,'value');
citra = double(handles.data1);

bitdepth = handles.bitdepth;
[m,n,~] = size(handles.data1);

if bitdepth == 8
    for i = 1:m
        for j = 1:n
            citra(i,j) = citra(i,j)+nilai_slider;
            if citra(i,j) > 255
                citra(i,j) = 255;
            end;
            if citra(i,j) < 0
                citra(i,j) = 0;
            end;
        end;
    end;
elseif bitdepth == 24
    for x = 1:3
        for i = 1:m
            for j = 1:n
                citra(i,j,x) = citra(i,j,x)+nilai_slider;
                if citra(i,j,x) > 255
                    citra(i,j,x) = 255;
                end;
                if citra(i,j,x) < 0
                    citra(i,j,x) = 0;
                end;
            end;
        end;
    end
else
    msgbox('Citra masukan harus grayscale atau RGB');
end

axes(handles.axes2);
gambar = uint8(citra);
imshow(gambar);

% --- Executes during object creation, after setting all properties.
function slider1_CreateFcn(hObject, eventdata, handles)
% hObject    handle to slider1 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    empty - handles not created until after all CreateFcns called

% Hint: slider controls usually have a light gray background.
if isequal(get(hObject,'BackgroundColor'), get(0,'defaultUicontrolBackgroundColor'))
    set(hObject,'BackgroundColor',[.9 .9 .9]);
end

6. Ketika di Run maka akan muncul tampilan seperti pada gambar berikut

7. Klik Buka Citra, pilih gambar yang ingin diproses

8. Geser slider ke arah terang

9. Geser silder ke arah gelap

File source code lengkap beserta citra pada pemrograman di atas dapat diperoleh melalui halaman berikut ini: Source Code

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