Problem for drawing on an image Matlab GUI

Hello ! I would like to create an interface where the user can upload on an image and draw on it and after save it. I already create the button which allowed the user to upload an image and another to save it. The functions works, now my problem is to draw on the image. I used buttondownfcn and windowbuttonmotionfcn to detect when the user clicks on the mouse and when he clicks I draw. These code works when the user draw next to the image but when I click on the image it doesn't works. It only works when I click next to the image. Please help me !!

 function varargout = IHM(varargin)

 Begin initialization code - DO NOT EDIT
 gui_Singleton = 1;
 gui_State = struct('gui_Name',       mfilename, ...
                   'gui_Singleton',  gui_Singleton, ...
                   'gui_OpeningFcn', @IHM_OpeningFcn, ...
                   'gui_OutputFcn',  @IHM_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 IHM is made visible.
 function IHM_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 IHM (see VARARGIN)
 % Choose default command line output for IHM
 handles.output = hObject;

 % Update handles structure
 guidata(hObject, handles);

 % UIWAIT makes IHM wait for user response (see UIRESUME)
 % uiwait(handles.figure1);
 setappdata(0  , 'LePath', gcf);

 % --- Outputs from this function are returned to the command line.
 function varargout = IHM_OutputFcn(hObject, eventdata, handles) 
 % varargout  cell array for returning output args (see VARARGOUT);

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

 % --- Executes on button press in OpenButton.
 function OpenButton_Callback(hObject, eventdata, handles)

 axes(handles.axes1);
 [Filename, Pathname] = uigetfile({'*.*'},'Select your picture(s)','MultiSelect','off');% recupere le chemin de l'image
 Chemin= Pathname;
 Chemin=strcat(Chemin, Filename);%concatene le chemin et le nom du fichier
 Foto=imread(Chemin); 

 %adapate les axes et redimensionne en fonction de la taille de l'image
 set(handles.axes1,'Units','pixels');
 resizePos = get(handles.axes1,'Position');
 Foto= imresize(Foto, [resizePos(3) resizePos(3)]);
 imshow(Foto);
 set(handles.axes1,'Units','normalized');
 axis manual;
 %conversion image dans un repère
 RI = imref2d(size(Foto));

 h = imshow(Foto,RI);

 LePath = getappdata(0, 'LePath');
 setappdata(LePath, 'PathName', Chemin);

 function DrawButton_Callback(hObject, eventdata, handles)
 % hObject    handle to DrawButton (see GCBO)
 % eventdata  reserved - to be defined in a future version of MATLAB
 % handles    structure with handles and user data (see GUIDATA)
 axis manual;
 %axis manual; %pour garder la taille des axes fixes (sinon tend vers infini  quand on draw)
 A=handles.axes1; % tag de l'axe

 set(A,'buttondownfcn',@start_pencil)%envoie vers la fonction start_pencil si on clique sur image

 function start_pencil(src,eventdata)
 coords=get(src,'currentpoint'); %récupère les info sur la position du  curseur
 x=coords(1,1,1);
 y=coords(1,2,1);

 r=line(x, y, 'color', [0 0 1], 'LineWidth', 2, 'hittest', 'off'); %turning      hittset off allows you to draw new lines that start on top of an existing line.
 set(gcf,'windowbuttonmotionfcn',{@continue_pencil,r})
 set(gcf,'windowbuttonupfcn',@done_pencil)

 function continue_pencil(src,eventdata,r)
 %Note: src is now the figure handle, not the axes, so we need to use gca.
 coords=get(gca,'currentpoint'); %this updates every time i move the mouse
 x=coords(1,1,1);
 y=coords(1,2,1);
 %get the line's existing coordinates and append the new ones.
 lastx=get(r,'xdata');  
 lasty=get(r,'ydata');
 newx=[lastx x];
 newy=[lasty y];
 set(r,'xdata',newx,'ydata',newy);

 function done_pencil(src,evendata)
 %all this funciton does is turn the motion function off 
 set(gcf,'windowbuttonmotionfcn','')
 set(gcf,'windowbuttonupfcn','')

 % --- Executes on button press in SaveButton.

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

 % sauvegarde de l'image 
 f = getframe(gca);
 im = frame2im(f);
 imwrite(im,'image2.png');

My code is in the attach file

Thank you

Rémy

Answer 1

[Geoff Hayes]

Rémy - try assigning the buttondownfcn to your handle to the image that you wish to draw upon. For example, in your OpenButton_Callback you would do

 handles.hImg = imshow(Foto,RI);
 guidata(hObject, handles);

So we update the handles structure with the handle to your image (presumably this is the one that you want to draw upon...it is unclear since you seem to show two images maybe on teh same axes?) and then we save the updated handles structure by calling guidata(...).

Now, in your DrawButton_Callback you would do

 set(handles.hImg,'buttondownfcn',{@start_pencil, handles.axes1})

Note how we assign the callback to the image handle and

 {@start_pencil, handles.axes1}

In the above, we are passing the axes handle as an additional parameter to the start_pencil callback. And so the start_pencil becomes

 function start_pencil(src,eventdata, hAxes)
 coords=get(hAxes,'currentpoint'); 
 % etc.

Try the above and see what happens!

I guess the real problem here is that the image is placed on top of your axes and so swallows the mouse button down event i.e. prevents the axes (beneath the image) from getting the mouse button down event. So we do the above so that the image acts upon the mouse button down event. Alternatively, you could leave your code as is and turn off the ability of the image to swallow/capture the mouse button down event

 set(handles.hImg, 'HitTest', 'off');

If you just add this one line of code, your app should work fine without the other changes discussed above. Please see Capturing Mouse Clicks for more details. In particular is the statement

HitTest — Determines if the object can respond to the mouse click it captures or passes the click to its closest ancestor.

[Geoff Hayes]

Rémy's answer moved here

Thank you very much ! I will try with your notes :)