今天，將介紹GUI中獲取圖像座標的最後一種方法—通過axes座標軸的回調函數實現座標的獲取。
今天使用的回調函數是axes中的ButtonDownFcn函數，當鼠標在axes中點擊時，MATLAB就會調用ButtonDownFcn函數。
下面是該GUI的gif圖：
下面貼出實現代碼：
function varargout = Getposition3(varargin)
% GETPOSITION3 MATLAB code for Getposition3.fig
% GETPOSITION3, by itself, creates a new GETPOSITION3 or raises the existing
% singleton*.
%
% H = GETPOSITION3 returns the handle to a new GETPOSITION3 or the handle to
% the existing singleton*.
%
% GETPOSITION3('CALLBACK',hObject,eventData,handles,...) calls the local
% function named CALLBACK in GETPOSITION3.M with the given input arguments.
%
% GETPOSITION3('Property','Value',...) creates a new GETPOSITION3 or raises the
% existing singleton*. Starting from the left, property value pairs are
% applied to the GUI before Getposition3_OpeningFcn gets called. An
% unrecognized property name or invalid value makes property application
% stop. All inputs are passed to Getposition3_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 Getposition3
% Last Modified by GUIDE v2.5 14-Apr-2019 12:00:42
% Begin initialization code - DO NOT EDIT
gui_Singleton = 1;
gui_State = struct('gui_Name', mfilename, ...
'gui_Singleton', gui_Singleton, ...
'gui_OpeningFcn', @Getposition3_OpeningFcn, ...
'gui_OutputFcn', @Getposition3_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 Getposition3 is made visible.
function Getposition3_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 Getposition3 (see VARARGIN)
% Choose default command line output for Getposition3
handles.output = hObject;
% Update handles structure
guidata(hObject, handles);
% UIWAIT makes Getposition3 wait for user response (see UIRESUME)
% uiwait(handles.figure1);
% --- Outputs from this function are returned to the command line.
function varargout = Getposition3_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)
% 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)
pic = imread('trees.tif');
handles.im = imshow(pic);
axis on
axes(handles.axes1);
set(handles.im,'Pickableparts','none');
set(handles.axes1,'ButtonDownFcn',@mycallbackfcn);
function mycallbackfcn(hObject,eventdata,handles)
handles = guidata(hObject);
pos = get(hObject,'Currentpoint');
set(handles.edit1,'string',pos(1,1));
set(handles.edit2,'string',pos(1,2));
function edit1_Callback(hObject, eventdata, handles)
% hObject handle to edit1 (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
% Hints: get(hObject,'String') returns contents of edit1 as text
% str2double(get(hObject,'String')) returns contents of edit1 as a double
% --- Executes during object creation, after setting all properties.
function edit1_CreateFcn(hObject, eventdata, handles)
% hObject handle to edit1 (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles empty - handles not created until after all CreateFcns called
% Hint: edit controls usually have a white background on Windows.
% See ISPC and COMPUTER.
if ispc && isequal(get(hObject,'BackgroundColor'), get(0,'defaultUicontrolBackgroundColor'))
set(hObject,'BackgroundColor','white');
end
function edit2_Callback(hObject, eventdata, handles)
% hObject handle to edit2 (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
% Hints: get(hObject,'String') returns contents of edit2 as text
% str2double(get(hObject,'String')) returns contents of edit2 as a double
% --- Executes during object creation, after setting all properties.
function edit2_CreateFcn(hObject, eventdata, handles)
% hObject handle to edit2 (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles empty - handles not created until after all CreateFcns called
% Hint: edit controls usually have a white background on Windows.
% See ISPC and COMPUTER.
if ispc && isequal(get(hObject,'BackgroundColor'), get(0,'defaultUicontrolBackgroundColor'))
set(hObject,'BackgroundColor','white');
end
% --- Executes during object creation, after setting all properties.
function pushbutton1_CreateFcn(hObject, eventdata, handles)
% hObject handle to pushbutton1 (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles empty - handles not created until after all CreateFcns called
一開始實現這個功能的時候，自己沒有發現這種方式實現，後面是在師兄的指導下實現的，其中最重要的就是設置圖像顯示句柄中的Pickableparts參數。
其中Pickableparts參數是確實對象是否捕獲鼠標點擊，同時HitTest參數是確定對象是否響應鼠標點擊或將其傳遞給最近的父級。
下面是這兩個參數設置時實現的功能：
具體詳情請看MATLAB公司的幫助文檔：https://ww2.mathworks.cn/help/matlab/creating_plots/capturing-mouse-clicks.html
通過這種方法實現雖然比前兩種方法都要好，但是還是存在一些缺點：
①因爲使用的是axes的回調函數，因此axis必須打開，當使用imshow函數時，必須使用axis on將axis打開（imshow默認關閉axis），而使用imagesc時axis默認打開；
②從gif圖中可以看出當獲取圖像外的座標區域時同樣也可以獲取座標信息，因爲座標區域仍然也是axes區域。
---------------------------------------------------------------------------------------------------------------------
雖然這三種方法都可以獲取GUI圖像上的座標，但是都存在缺點，如果大家有更好的辦法，希望能分享，最後祝大家在學習的道路上一帆風順~