How to load the latest picture automatically

I have a program to vertically integrate the intensity of pictures. There is a push button that allows me to load the latest the picture in the directory. However, if I just run the program, no file is loaded at the beginning. I am wondering if there is a way to automatically load the latest file when I click run the program. Thanks!

   function photobooth

   defaultfileDir = 'C:\Users\physlabuser\Pictures\Camera Roll';  %This path 
directory changes to reflect user
   %defaultfileDir = [pwd, 'C:\Users\physlabuser\Pictures\Camera Roll'];

   default_ub = 300;
   default_lb = 200;

   buttonHeight = 0.03;
   buttonWidth = 0.08;
   spacing = 0.01;
   row1 = 0.94;
   row2 = 0.90;
   row3 = 0.86;
   row4 = 0.82;
   row5 = 0.78;
   panelHeight = (row1 - row5) + 3*spacing + buttonHeight;
   browseWidth = 0.04;
   % specific to ROI section
   col0 = 0.95 - buttonWidth - 2*spacing - browseWidth - 0.38;
   col05 = (col0 + buttonWidth + spacing);
   col1 = 0.95 - buttonWidth - spacing - browseWidth;
   col2 = 0.95 - buttonWidth;
   fieldWidth = 0.12;
   nameWidth = 0.38 - buttonWidth - spacing;
   panelWidth = (col2 - col0) + 2*spacing + buttonWidth;
   % specific to fitting section
   structWidth = 4*buttonWidth + 2*spacing - browseWidth - spacing;
   fcol0 = 0.05;
   fcol1 = 0.05 + buttonWidth + spacing;
   fcol2 = 0.05 + 2*buttonWidth + 2*spacing;
   fbrowsecol = fcol1 + structWidth + spacing;
   fcol3 = fbrowsecol + browseWidth + spacing;
   fpanelWidth = (fcol3 - fcol0) + 2*spacing + buttonWidth;

   mainX = 0.05;
   mainY = 0.3;
   mainW = 0.9;
   mainH = 0.55;

   histX = 0.05;
   histY = 0.05;
   histW = 0.9;
   histH = 0.2;

   hMainFigure = figure(...
            'Visible','off',...
            'NumberTitle','off',...
            'Name','Some random vertically integrating program',...
            'Toolbar','figure',...
            'Position',[128,128,864,864]);

   %Make the GUI visible.
   set(hMainFigure,'Visible','on')

   %  Construct the components
   ah         = axes(...
           'Parent',hMainFigure,...
           'ButtonDownFcn', @get_cursor_pos, ...
           'Position',[mainX mainY mainW mainH]);

   histogram  = axes(...
           'Parent',hMainFigure,...
           'Position',[histX histY histW histH]);

   imagefieldtext = uicontrol(...
            'Parent', hMainFigure, ...
            'Units','normalized',...
            'Style', 'text', ...
            'String','image location',...
            'HorizontalAlignment', 'center', ...
            'Position',[fcol0 row1 buttonWidth buttonHeight]);

   imagefield = uicontrol(...
           'Style','edit',...
           'Parent', hMainFigure, ...
           'String','' ,...
           'Units','normalized',...
           'Max',1,'Min',0,...
           'Callback', @UpdateCallback,...
           'Position',[fcol1 row1 structWidth buttonHeight]);

   imageBrowseButton = uicontrol(...    % button for updating selected plot 
           'Parent', hMainFigure, ...
           'Units','normalized',...
           'HandleVisibility','callback', ...
           'Position',[fbrowsecol row1 browseWidth buttonHeight],...
           'String','...',...
           'Callback', @imageBrowseCallback);

   loadLatestButton = uicontrol(...    % button for updating selected plot 
           'Parent', hMainFigure, ...
           'Units','normalized',...
           'HandleVisibility','on',...
           'Position',[fcol3 row1 buttonWidth buttonHeight],...
           'String','Load Latest',...
           'Callback', @loadLatestImage);

   fileDirtext = uicontrol(...
            'Parent', hMainFigure, ...
            'Units','normalized',...
            'Style', 'text', ...
            'String','Camera Roll dir',...
            'HorizontalAlignment', 'center', ...
            'Position',[fcol0 row2 buttonWidth buttonHeight]);

   fileDirField = uicontrol(...
           'Style','edit',...
           'Parent', hMainFigure, ...
           'String',defaultfileDir,...
           'Units','normalized',...
           'Max',1,'Min',0,...
           'Callback', @fileDirUpdateCallback,...
           'Position',[fcol1 row2 structWidth buttonHeight]);

   fileDirBrowseButton = uicontrol(...    % button for updating selected plot 
           'Parent', hMainFigure, ...
           'Units','normalized',...
           'HandleVisibility','callback', ...
           'Position',[fbrowsecol row2 browseWidth buttonHeight],...
           'String','...',...
           'Callback', @hfileDirBrowseCallback);

   directionstext = uicontrol(...
            'Parent', hMainFigure, ...
            'Units','normalized',...
            'Style', 'text', ...
            'String','use cursor to select point and then hit "Set lb" ("Set ub") to specify lower (upper) integration bounds.',...
            'HorizontalAlignment', 'center', ...
            'Position',[col0 + 2*buttonWidth row2 0.2 2*buttonHeight + spacing]);

   lbButton = uicontrol(...    % button for updating selected plot 
           'Parent', hMainFigure, ...
           'Units','normalized',...
           'HandleVisibility','callback', ...
           'Position',[col2 row1 buttonWidth buttonHeight],...
           'String','Set lb',...
           'Callback', @getlb);

   ubButton = uicontrol(...    % button for updating selected plot 
           'Parent', hMainFigure, ...
           'Units','normalized',...
           'HandleVisibility','callback', ...
           'Position',[col2 row2 buttonWidth buttonHeight],...
           'String','Set ub',...
           'Callback', @getub);

   lbfield = uicontrol(...    % button for updating selected plot 
           'Style','edit',...
           'Parent', hMainFigure, ...
           'Units','normalized',...
           'HandleVisibility','callback', ...
           'Position',[col1 row1 browseWidth buttonHeight],...
           'String',num2str(default_lb),...
           'Callback', @loadImage);

   ubfield = uicontrol(...    % button for updating selected plot 
           'Style','edit',...
           'Parent', hMainFigure, ...
           'Units','normalized',...
           'HandleVisibility','callback', ...
           'Position',[col1 row2 browseWidth buttonHeight],...
           'String',num2str(default_ub),...
           'Callback', @loadImage);

   data = guihandles(hMainFigure); 
   data.fileDir = defaultfileDir;
   data.ub = default_ub;
   data.lb = default_lb;
   guidata(hMainFigure, data) 
   %%%%%%%callbacks %%%%%%%%%

   function hfileDirBrowseCallback(hObject, eventdata)   
   % Callback function run when the update button is pressed
    foldername = uigetdir(pwd, ...
        'Select Photo Booth directory.');
    if foldername == 0
    else
        set(fileDirField, 'String', foldername);
        data = guidata(gcbo);
        data.fileDir = foldername;
        guidata(gcbo, data);
    end
   end

   function UpdateCallback(hObject, eventdata)   
   % Callback function run when the update button is pressed
    loadImage(imagefield, eventdata)
   end

   function fileDirUpdateCallback(hObject, eventdata)   
   % Callback function run when the update button is pressed
    foldername = get(fileDirField, 'String');
    data = guidata(gcbo);
    data.fileDir = foldername;
    guidata(gcbo, data);
   end

   function imageBrowseCallback(hObject, eventdata)   
   % Callback function run when the update button is pressed
    data = guidata(gcbo);
    [filename pathname] = uigetfile(fullfile(data.fileDir, '*.jpg'), ...
        'Select image to display.');
    if filename == 0
    else
        imagename = fullfile(pathname, filename);
        set(imagefield, 'String', imagename);
        loadImage(imagefield, eventdata)
    end
   end

   function loadLatestImage(hObject, eventdata)   
   % Callback function run when the update button is pressed
    data = guidata(gcbo);
    files = dir(fullfile(data.fileDir,'*.jpg'));

    if numel(files) == 0
        warndlg('No JPG files exist in Camera Roll directory.')
    else
        dates = [files(:).datenum];

        [sorted_dates date_order] = sort(dates);
        sorted_files = files(date_order);
        files = sorted_files;

   %        for i = 1:numel(files)
   %        disp('---------new image---------')
   %          files(i).name
   %          files(i).date
   %          files(i).datenum
   %        end
   %
        set(imagefield, 'String', fullfile(data.fileDir, files(end).name));
        loadImage(imagefield, eventdata)
    end
   end

   function get_cursor_pos(hObject, eventdata)
    cursor_pos = get(ah, 'Currentpoint');
   end

   function getub(hObject, eventdata)
    cursor_pos = get(ah, 'Currentpoint');
    set(ubfield, 'String', num2str(round(cursor_pos(1, 2, 1))));
    data = guidata(gcbo);
    data.ub = str2num(get(ubfield, 'String'));
    guidata(gcbo, data);

    loadImage(imagefield, eventdata)
   end

   function getlb(hObject, eventdata)
    cursor_pos = get(ah, 'Currentpoint');
    set(lbfield, 'String', num2str(round(cursor_pos(1, 2, 1))));
    data = guidata(gcbo);
    data.lb = str2num(get(lbfield, 'String'));
    guidata(gcbo, data);

    loadImage(imagefield, eventdata)
   end

   function loadImage(field, eventdata)
    imagename = get(imagefield, 'String');
    [X map] = imread(imagename);
    %imagesc(X, 'Parent', ah, 'HitTest', 'off')
    imagesc(X, 'Parent', ah);
    set(ah, 'ButtonDownFcn', @get_cursor_pos);

    data = guidata(gcbo);
    data.lb = str2num(get(lbfield, 'String'));
    data.ub = str2num(get(ubfield, 'String'));
    guidata(gcbo, data);

    if data.lb > 0 && data.ub > 0
        vert_hist = sum(X(data.lb:data.ub, :, 1), 1);
        vert_hist = vert_hist + sum(X(data.lb:data.ub, :, 2), 1);
        vert_hist = vert_hist + sum(X(data.lb:data.ub, :, 3), 1);
        plot(vert_hist, 'Parent', histogram);
        axes(histogram)
        axis tight
    end
   end

   end

Answer 1

[Walter Roberson]

After you call

     guidata(hMainFigure, data)

then call

loadLatestImage(loadLatestButton, [])

and in loadLatestImage change

data = guidata(gcbo);

to

data = guidata(hObject);

(because for that direct call there will not be a callback object.)

[JP]

Thank you very much! It works!