上次講的是通過ginput函數進行GUI中圖像座標的獲取，但是該方法存在很多缺點，如美觀、可以獲取圖像外部區域等問題。今天，我將介紹一個較ginput函數較好的GUI上圖像座標獲取函數：datacursormode函數。
今天介紹的函數datacursormode其實是圖窗上數據遊標模式的啓用函數，詳細使用方式見MATLAB幫助文檔：
其實數據遊標模式大家肯定經常見，下面就是這種模式打開的狀態：
圖像上面會顯示遊標所在點的一個信息。
下面的Gif圖就是使用datacursor函數獲取圖像座標的GUI：
下面是實現代碼：
function varargout = Getposition2(varargin)
% GETPOSITION2 MATLAB code for Getposition2.fig
% GETPOSITION2, by itself, creates a new GETPOSITION2 or raises the existing
% singleton*.
%
% H = GETPOSITION2 returns the handle to a new GETPOSITION2 or the handle to
% the existing singleton*.
%
% GETPOSITION2('CALLBACK',hObject,eventData,handles,...) calls the local
% function named CALLBACK in GETPOSITION2.M with the given input arguments.
%
% GETPOSITION2('Property','Value',...) creates a new GETPOSITION2 or raises the
% existing singleton*. Starting from the left, property value pairs are
% applied to the GUI before Getposition2_OpeningFcn gets called. An
% unrecognized property name or invalid value makes property application
% stop. All inputs are passed to Getposition2_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 Getposition2
% Last Modified by GUIDE v2.5 11-Apr-2019 16:36:13
% Begin initialization code - DO NOT EDIT
gui_Singleton = 1;
gui_State = struct('gui_Name', mfilename, ...
'gui_Singleton', gui_Singleton, ...
'gui_OpeningFcn', @Getposition2_OpeningFcn, ...
'gui_OutputFcn', @Getposition2_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 Getposition2 is made visible.
function Getposition2_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 Getposition2 (see VARARGIN)
% Choose default command line output for Getposition2
handles.output = hObject;
% Update handles structure
guidata(hObject, handles);
% UIWAIT makes Getposition2 wait for user response (see UIRESUME)
% uiwait(handles.figure1);
% --- Outputs from this function are returned to the command line.
function varargout = Getposition2_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');
axes(handles.axes1)
imagesc(pic);
for i=1:10
dcm_obj =datacursormode(gcf);
set(dcm_obj,'DisplayStyle','datatip','Enable','on')
pause
c_info = getCursorInfo(dcm_obj);
pos = c_info.Position;
set(handles.edit1,'string',pos(2));
set(handles.edit2,'string',pos(1));
end
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
通過這種方法獲取GUI圖像上的點的座標有優點也有缺點：
優點：
①這個方法只可以獲取顯示圖像範圍內的座標點，同時顯示的座標爲圖像上點的真實座標。上一篇介紹ginput函數時，大家可能注意到了獲取的座標爲小數，因爲ginput函數獲取的座標是figure上的連續座標，而本文中介紹的datacursormode函數獲取的是顯示圖像上的離散座標點；
②選取的點的信息可以通過datatip顯示在圖像上
缺點：
①使用datacursormode函數前必須預先設置選取點的個數，因爲在獲取datacursormode函數的信息前，必須通過pause等函數進行中斷才能正確獲取其信息。
②也可以通過while和try catch來實現，但是使用死循環，會可能使程序崩了；
③當使用pause中斷時，沒有點夠相應數目的點就退出程序會出現錯誤。
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因爲自己沒有很好的利用MATLAB公司推出的幫助文檔，該方法的實現過程很坎坷~
因此希望大家在嘗試使用新函數時，一定要仔細查看MATLAB公司的幫助文檔~
祝大家在學習的道路上一帆風順~