MATLAB: Problems reading points from image loaded into guide GUI

createfcnguiguideImage Processing Toolboximreadimshowopeningfcn

Hi,
I made a GUI to display an image and retrieve current point when clicked. I did this in 3 slightly different ways, but don't know why they work/don't work in each case. Could someone help explain why..?
Case 1: 'pts' is displayed in command window
function varargout = Atest2(varargin)
% Begin initialization code - DO NOT EDIT


gui_Singleton = 1;
gui_State = struct('gui_Name',       mfilename, ...
                   'gui_Singleton',  gui_Singleton, ...
                   'gui_OpeningFcn', @Atest2_OpeningFcn, ...
                   'gui_OutputFcn',  @Atest2_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


function Atest2_OpeningFcn(hObject, eventdata, handles, varargin)
handles.output = hObject;
guidata(hObject, handles);
function varargout = Atest2_OutputFcn(hObject, eventdata, handles) 
varargout{1} = handles.output;
function axes1_CreateFcn(hObject, eventdata, handles)
Im = imagesc(imread('test.jpg'));
set(Im,'HitTest','Off')
set(hObject,'ButtonDownFcn',@axes1_ButtonDownFcn)
function axes1_ButtonDownFcn(hObject, eventdata, handles)
pts = hObject.CurrentPoint
Case 2: 'pts' is NOT displayed in command window (only difference: imshow instead of imagesc /imread)
function varargout = Atest2(varargin)
% Begin initialization code - DO NOT EDIT
gui_Singleton = 1;
gui_State = struct('gui_Name',       mfilename, ...
                   'gui_Singleton',  gui_Singleton, ...
                   'gui_OpeningFcn', @Atest2_OpeningFcn, ...
                   'gui_OutputFcn',  @Atest2_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
function Atest2_OpeningFcn(hObject, eventdata, handles, varargin)
handles.output = hObject;
guidata(hObject, handles);
function varargout = Atest2_OutputFcn(hObject, eventdata, handles) 
varargout{1} = handles.output;
function axes1_CreateFcn(hObject, eventdata, handles)
Im = imshow('test.jpg');
set(Im,'HitTest','Off')
set(hObject,'ButtonDownFcn',@axes1_ButtonDownFcn)
function axes1_ButtonDownFcn(hObject, eventdata, handles)
pts = hObject.CurrentPoint
Case 3: Code in 'createfcn' moved to 'openingfcn'. Pts displays in command window, but now with only 2 arguments instead of 6.
function varargout = Atest2(varargin)
% Begin initialization code - DO NOT EDIT
gui_Singleton = 1;
gui_State = struct('gui_Name',       mfilename, ...
                   'gui_Singleton',  gui_Singleton, ...
                   'gui_OpeningFcn', @Atest2_OpeningFcn, ...
                   'gui_OutputFcn',  @Atest2_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
function Atest2_OpeningFcn(hObject, eventdata, handles, varargin)
handles.output = hObject;
guidata(hObject, handles);
Im = imshow('test.jpg');
set(Im,'HitTest','Off')
set(hObject,'ButtonDownFcn',@axes1_ButtonDownFcn)
function varargout = Atest2_OutputFcn(hObject, eventdata, handles) 
varargout{1} = handles.output;
function axes1_CreateFcn(hObject, eventdata, handles)
function axes1_ButtonDownFcn(hObject, eventdata, handles)
pts = hObject.CurrentPoint
It seems almost as if there's a bug in my software..? (I'm using a free trial of Matlab 2014b (8.4.0.150421), on MacBook Air, OS X Yosemite 10.10.1.)

Best Answer

Lyn - for your third case,
 function Atest2_OpeningFcn(hObject, eventdata, handles, varargin)
 handles.output = hObject;
 guidata(hObject, handles);
 Im = imshow('test.jpg');
 set(Im,'HitTest','Off')
 set(hObject,'ButtonDownFcn',@axes1_ButtonDownFcn)
hObject is the figure and not the axes, so that will (probably) explain why you are observing only an (x,y) coordinate rather than the two (x,y,z) coordinates. If you want this code to be similar to the other cases, then you would have to supply the handle to the axes like
 set(handles.axes1,'ButtonDownFcn',@axes1_ButtonDownFcn)
As for the other cases behaving differently, try running the following line of code after each call to set the hit test value
 set(Im,'HitTest','Off')
 get(Im,'type')
For the use of imagesc, the type should be image. What is the type for Im when imshow is used? It may be that you are disabling the hit test for something other than the image (the axes perhaps?).
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