Showing Alert of empty axes box.

When the Axes Box does not contain any image and user clicks on the Push button then an error should popup saying "Please upload an image" or something else, how to do that how check whether the axes box is empty or not?

[Jan]

Please provide any details. Show us the relevant part of the code, e.g. the button's callback. Do you have the handle of the axes? Does the axes contain any other child objects? What about setting a flag, when the image is imported?

[Rya]

like this is main screen, i want to put a check that when user doesn't go in proper order i.e click on 'matching' at first it should make alert that upload image first similar case with 'Extract no plate' button

Answer 1

[Walter Roberson]

Set the 'enable' property of the Extract button to 'off' at the start of the program. When the user has uploaded or captured an image, set the enable property to 'on'. That way it is not possible for the Extract button to be clicked when there is no image to extract from.

[Rya]

how to do it programmatically, so that it happens automatically at run time

[Jan]

It is much easier to post the required additions to your code, if we see your code.

[Walter Roberson]

   function extract_button_CreateFcn(hObject, event, varargin)
     set(hObject, 'Enable', 'off');

function upload_button_Callback(hObject, event, handles)
   .....
   set(handles.extract_button, 'Enable', 'on');

[Walter Roberson]

function Load_Callback(hObject, eventdata, handles)

[filename, pathname]=uigetfile({'*.jpg';'*.jpeg';'*.gif';'*.png';'*.bmp'},'Select file'); 

global MyImage;

MyImage = fullfile(pathname, filename);

im = imread(MyImage); 

imshow(im, 'Parent', handles.axes1);

set(handles.Extract, 'enable', 'on')

function Extract_CreateFcn(hObject, eventdata, varargin)

set(hObject, 'enable', 'off')

function Extract_Callback(hObject, eventdata, handles)

global MyImage;

global noPlate;

%no need to test if the axes is empty, because we do not enable
%the button until it is loaded

numberPlateExtraction(MyImage);

set(handles.edit1, 'string', noPlate);

[Rya]

Thank You so very much it works but it only works when i first run the application i want to show a alert box so each time when users pushes any action button it alerts to load image before extracting

[Walter Roberson]

You seem to be implying that this code worked for you exactly once, but never again?? Did you make sure to tell GUIDE that you wanted to use a Create callback, and did you save your changes in GUIDE?

Alternately, perhaps you are implying that there is some action that the user can take while using the program that should result in the condition being reset? Because once they have loaded an image once, they have loaded an image so telling them that they need load an image first would seem to be the wrong thing to do?

[Rya]

yes i made changes in guide also, it still does not work and this is not according to my requirement as well, let me clear u . if there is no image in axes, then clicking on Action buttons like 'extract' and 'match' is something nonsense, i want to alert the user of my project whenever he clicks on any action(button) before loading image a msgbox must popup to alert a user

[Walter Roberson]

function Load_Callback(hObject, eventdata, handles)

[filename, pathname]=uigetfile({'*.jpg';'*.jpeg';'*.gif';'*.png';'*.bmp'},'Select file'); 

global MyImage;

MyImage = fullfile(pathname, filename);

im = imread(MyImage); 

imshow(im, 'Parent', handles.axes1);

handles.have_loaded_something = 1;
guidata(hObject, handles);

function Extract_Callback(hObject, eventdata, handles)

global MyImage;

global noPlate;

if ~isfield(handles, 'have_loaded_something')
  handles.have_loaded_something = 0;
  guidata(hObject, handles);
end

if ~handles.have_loaded_something
   msgbox('You need to load an image!', 'modal');
   return
end

numberPlateExtraction(MyImage);

set(handles.edit1, 'string', noPlate);

Answer 2

[Adam]

Declare e.g.

handles.hImage = [];

at the start of your program, then just set this when you plot the image as e.g.

handles.hImage = imagesc( hAxes,... );

Then in your pushbutton callback you can just test

if isempty( handles.hImage )
   errordlg( 'Please upload an image' )
   return
end

[Rya]

what is hImage?

[Adam]

The handle to your image graphics object

[Rya]

means handles.axes ??

[Adam]

No, it is the image. In my example I used imagesc when plotting and assigning it. You may be using imshow or some other image plotting function.

What I called hAxes would be your handles.axes or whatever its tag is.

[Rya]

can u send me your mail address?

[Adam]

I only answer questions on the forum as and when time allows.

[Rya]

okay but this code doesn't work i tried this code

if get(0,'CurrentFigure')

end

it works for both when axes is empty and when filled with image.

[Adam]

It is pseudo code as it stands to give an example. I don't know what your code includes.

[Rya]

i got u and i've turned it into my code but may be i did wrong somewhere should i send u my code?

[Adam]

Just paste in the relevant parts or attach it in your question or a comment to the question.

[Jan]

@Rya: Please post the relevant of the code here. Then it would be easy to suggest the modifications. Without seeing the code, we have to guess what might match and as you see this provokes many misunderstandings.

The screenshot of the GUI does not help. We really need the relevant part of the code. Thanks.

[Rya]

what should i post? i have done nothing regarding to this .... as i m confused still i post few of code, tell me if it works

function Load_Callback(hObject, eventdata, handles)

[filename, pathname]=uigetfile({'*.jpg';'*.jpeg';'*.gif';'*.png';'*.bmp'},'Select file'); 

global MyImage;

   MyImage = strcat(pathname, filename);

   im=imread(MyImage); 

imshow(im,'Parent',handles.axes1);

function Extract_Callback(hObject, eventdata, handles)

global MyImage;

global noPlate;

********if axes is empty*******

% if get(0,'CurrentFigure')

   % if the axes is empty

% warndlg('Please Upload an Image','Upload Image');

% elseif 

numberPlateExtraction(MyImage);

set(handles.edit1,'string',noPlate);

[Adam]

You said you had tried incorporating my answer into your code. Obviously it won't work if you haven't actually changed anything!

[Rya]

here i implemented ur code , plz give a look and tell me where i did a mistake

function varargout = Main(varargin)

handles.MyImage = [];

handles.MyImage = imshow( handles.axes,... );

gui_Singleton = 1;

gui_State = struct('gui_Name', mfilename, ... 'gui_Singleton', gui_Singleton, ... 'gui_OpeningFcn', @Main_OpeningFcn, ... 'gui_OutputFcn', @Main_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

function Main_OpeningFcn(hObject, eventdata, handles, varargin)

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

guidata(hObject, handles);

function varargout = Main_OutputFcn(hObject, eventdata, handles)

function Loadimage_Callback(hObject, eventdata, handles)

[filename, pathname]=uigetfile( {'*.jpg';'*.jpeg';'*.gif';'*.png';'*.bmp'},'Select file');

 global MyImage;

 MyImage = strcat(pathname, filename);

        if isequal(filename,0) || isequal(pathname,0)
            uiwait(msgbox ('Load Image required','failed','modal')  )
            hold on;
        end
        im=imread(MyImage);

        im=im2double(im); %converts to double

imshow(im,'Parent',handles.axes1);

function Extract_Callback(hObject, eventdata, handles)

if isempty( handles.MyImage ) errordlg( 'Please upload an image' ) return end global MyImage;

global noPlate;

numberPlateExtraction(MyImage);

set(handles.edit1,'string',noPlate);

[Image Analyst]

Why not simply use getimage() like I suggested to find out if there is any image in the axes???

[Rya]

where should i write in call back function? plz implement your example in above given code

Answer 3

[Image Analyst]

You can use getimage() to see if there is any image in the axes. It will be empty if you have not loaded an image yet (with a function such as imshow, image, imagesc, etc.). Use axes() to switch the current axes to the one you care about, then:

theImage = getimage();
if isempty(theImage)
    % Nothing is in the current axes.
    uiwait(warndlg('Please load an image'));
end