Why did I this error Error in Matlab_Partical_fig1 (line 43).

I don't understand why my brighten push button and darken buttion don't work?

function varargout = Matlab_Partical_fig1(varargin)
B = 1
% MATLAB_PARTICAL_FIG1 MATLAB code for Matlab_Partical_fig1.fig
%      MATLAB_PARTICAL_FIG1, by itself, creates a new MATLAB_PARTICAL_FIG1 or raises the existing
%      singleton*.
%
%      H = MATLAB_PARTICAL_FIG1 returns the handle to a new MATLAB_PARTICAL_FIG1 or the handle to
%      the existing singleton*.
%
%      MATLAB_PARTICAL_FIG1('CALLBACK',hObject,eventData,handles,...) calls the local
%      function named CALLBACK in MATLAB_PARTICAL_FIG1.M with the given input arguments.
%
%      MATLAB_PARTICAL_FIG1('Property','Value',...) creates a new MATLAB_PARTICAL_FIG1 or raises the
%      existing singleton*.  Starting from the left, property value pairs are
%      applied to the GUI before Matlab_Partical_fig1_OpeningFcn gets called.  An
%      unrecognized property name or invalid value makes property application
%      stop.  All inputs are passed to Matlab_Partical_fig1_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 Matlab_Partical_fig1

% Last Modified by GUIDE v2.5 14-Mar-2024 13:23:49

% Begin initialization code - DO NOT EDIT
gui_Singleton = 1;
gui_State = struct('gui_Name',       mfilename, ...
                   'gui_Singleton',  gui_Singleton, ...
                   'gui_OpeningFcn', @Matlab_Partical_fig1_OpeningFcn, ...
                   'gui_OutputFcn',  @Matlab_Partical_fig1_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 Matlab_Partical_fig1 is made visible.
function Matlab_Partical_fig1_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 Matlab_Partical_fig1 (see VARARGIN)

% Choose default command line output for Matlab_Partical_fig1
handles.output = hObject;

% Update handles structure
guidata(hObject, handles);
% UIWAIT makes Matlab_Partical_fig1 wait for user response (see UIRESUME)
% uiwait(handles.figure1);


% --- Outputs from this function are returned to the command line.
function varargout = Matlab_Partical_fig1_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)
handles.filename = uigetfile('*.jpg');
handles.theOriginalImage = imread(handles.filename);
handles.theNewImage = handles.theOriginalImage;
image(handles.theOriginalImage);
guidata(hObject, 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)


% --- Executes on button press in checkbox1.
function checkbox1_Callback(hObject, eventdata, handles)
% hObject    handle to checkbox1 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)

% Hint: get(hObject,'Value') returns toggle state of checkbox1
isChecked = get(hObject,'Value');
if(isChecked)
    image(handles.theOriginalImage);
else
    image(handles.theNewImage);
end

% --- Executes on button press in pushbutton2 Darken Button
function pushbutton2_Callback(hObject, eventdata, handles)
Ft = B ;
Sv = (Ft-.25)/Ft;
Nt = Sv * Ft ;
B = Nt
handles.theNewImage = handles.theNewImage .* (B)
image(handles.theNewImage);
guidata(hObject,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)


% --- Executes on button press in pushbutton3 Lighten Button
function pushbutton3_Callback(hObject, eventdata, handles)
Ft = B ;
Av = (Ft+.25)/Ft;
Nt = Av * Ft;
B = Nt
handles.theNewImage = handles.theNewImage .* (B)
image(handles.theNewImage);
guidata(hObject,handles);
% hObject    handle to pushbutton3 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)


% --- Executes on button press in pushbutton5 Removes Color
function pushbutton5_Callback(hObject, eventdata, handles)
[row col pan] = size(handles.theNewImage);
for J = 1:row
    for K = 1:col
        averagedVal = (handles.theNewImage(J,K,1) +handles.theNewImage(J,K,2) +handles.theNewImage(J,K,3))/3;
        handles.theNewImage(J,K,1) = averagedVal;
        handles.theNewImage(J,K,2) = averagedVal;
        handles.theNewImage(J,K,3) = averagedVal;
    end
end

image(handles.theNewImage);
guidata(hObject,handles);
% hObject    handle to pushbutton5 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)


% --- Executes on button press in pushbutton6 Save As
function pushbutton6_Callback(hObject, eventdata, handles)
[fileName, pathName] = uiputfile({'*.jpg', 'JPEG Image (*.jpg)'; '*.png', 'PNG Image (*.png)'}, 'Save As');
filePath = fullfile(pathName, fileName);
imwrite(handles.theNewImage, filePath);

% hObject    handle to pushbutton4 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)

% --- Executes on button press in pushbutton8. Color Swap
function pushbutton8_Callback(hObject, eventdata, handles)
handles.theNewImage(:,:,1) = handles.theNewImage(:,:,2); 
handles.theNewImage(:,:,2) = handles.theNewImage(:,:,3); 
handles.theNewImage(:,:,3) = handles.theNewImage(:,:,1);
image(handles.theNewImage);
guidata(hObject,handles);
% hObject    handle to pushbutton8 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)


% --- Executes on button press in pushbutton11. NO Red
function pushbutton11_Callback(hObject, eventdata, handles)
handles.theNewImage(:,:,1) = 0;
image(handles.theNewImage);
guidata(hObject,handles);
% hObject    handle to pushbutton11 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)


% --- Executes on button press in pushbutton12 reset
function pushbutton12_Callback(hObject, eventdata, handles)
handles.theNewImage = handles.theOriginalImage;
image(handles.theNewImage);
guidata(hObject,handles);
% hObject    handle to pushbutton12 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)

Answer 1

[Voss]

function pushbutton2_Callback(hObject, eventdata, handles)
Ft = B ;

B is not defined in that function.

B is defined in the main function:

function varargout = Matlab_Partical_fig1(varargin)
B = 1

but the callbacks are all local functions (a.k.a. subfunctions of the main function) with their own workspaces, so you'd need to define B in each function where you want to use it, or better, put it in the handles structure and use that.

https://www.mathworks.com/help/matlab/matlab_prog/local-functions.html

[Voss]

How to put B in the handles structure and use it:

1. Modify the Opening Function to store B in the handles structure:

% --- Executes just before Matlab_Partical_fig1 is made visible.
function Matlab_Partical_fig1_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 Matlab_Partical_fig1 (see VARARGIN)
% Choose default command line output for Matlab_Partical_fig1
handles.output = hObject;

handles.B = 1;

% Update handles structure
guidata(hObject, handles);
% UIWAIT makes Matlab_Partical_fig1 wait for user response (see UIRESUME)
% uiwait(handles.figure1);

2. Anywhere you want to use that B, refer to handles.B:

% --- Executes on button press in pushbutton2 Darken Button
function pushbutton2_Callback(hObject, eventdata, handles)
Ft = handles.B ;
Sv = (Ft-.25)/Ft;
Nt = Sv * Ft ;
B = Nt
handles.theNewImage = handles.theNewImage .* (B)
image(handles.theNewImage);
guidata(hObject,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)