MATLAB: How to display 10 images on a MATLAB GUI and then drag and drop each of them individually in order to arrange them in a particular order

drag and drop imagesmatlab gui

Hi,

I need to display 10 different images simultaneously on a MATLAB GUI using 10 different axes graphical object. Then each of these images needs to be drag and drop in the GUI in order to make a particular arrangement. I have used drag_n_drop.m function found on the internet with some modifications. I can drag and drop a single axes with out images by using this. Once I add an images, it is producing 'Reference to non-existent field 'axes1'' error message. I am attaching the drag_n_drop function and the GUI opening function, which I have for this purpose.

function drag_n_drop(fig_handle, eventdata)
%Get position of Mouse location in figure
%handles.output = hObject;
handles = guihandles(fig_handle);
pos = get(fig_handle, 'currentpoint');  % get mouse location on figure
x = pos(1); y = pos(2);                 % assign locations to x and y
% get position information of the uicontrol
bounds = get(handles.axes1,'position');
lx = bounds(1); ly = bounds(2);
lw = bounds(3); lh = bounds(4);
% test to see if mouse is within the uicontrol and make a hand sign
if x >= lx && x <= (lx + lw) && y >= ly && y <= (ly + lh)
    setfigptr('hand', handles.figure1);
    set(handles.axes1, 'ButtonDownFcn', @grab);
    else
    setfigptr('arrow', handles.figure1);
   end
function grab(target_handle, eventData)
        % to be attached to ButtonDownFcn of the uicontrol 
        % change the shape of the pointer to closed hand
        setfigptr('closedhand', fig_handle);         
          % computing x, y difference between pointer and uicontrol 
          % so that the movement can be in sync
          mouse_pos = get(fig_handle, 'currentpoint'); 
          target_pos = get(handles.axes1,'position');
          dx = mouse_pos(1) - target_pos(1);
          dy = mouse_pos(2) - target_pos(2);
          % attach drag and release to WindowButtonMotionFcn and
          % WindowButtonUpFcn
          set(fig_handle,'WindowButtonMotionFcn', @drag);   
          set(fig_handle,'WindowButtonUpFcn',@release);
          function drag(fig_handle, eventData)
              % to be attached to WindowButtonMotionFcn
              % get mouse x,y location on figure
              mouse_pos = get(fig_handle, 'currentpoint'); 
              x = mouse_pos(1); y = mouse_pos(2); 
              % get uicontrol width and height
              target_pos = get(handles.axes1,'position');
              tw = target_pos(3); th = target_pos(4);
              % update uicontrol position based on the computed x,y locations
              target_pos = [x-dx, y-dy, tw, th];
              set(handles.axes1,'position', target_pos);
          end % end of drag function 
          function release(fig_handle, eventData)
              % to be attached to WindowButtonUpFcn
              % update pointer back to hand shape 
              setfigptr('hand', fig_handle);
              mouse_pos = get(fig_handle, 'currentpoint'); 
              x = mouse_pos(1); y = mouse_pos(2);            
              set(fig_handle, 'WindowButtonMotionFcn', @drag_and_drop);
              set(fig_handle, 'WindowButtonUpFcn', '');
          end % end of release function 
          end % end of grab function 
      end % end of drag_and_drop function

GUI Opening Function

% --- Executes just before rank is made visible.
function rank_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 rank (see VARARGIN)
% Choose default command line output for rank
axes(handles.axes1);
img=imread('camo_part.jpg');
imshow(img);
handles.output = hObject;
set(hObject,'WindowButtonMotionFcn',@drag_n_drop);
% Update handles structure
guidata(hObject, handles);
% UIWAIT makes rank wait for user response (see UIRESUME)
% uiwait(handles.figure1);
end

I can drag and drop blank axes using this function. But when I add an image into the axes object, this code produces an error "Reference to non-existent field 'axes1' ". Please suggest if I can avoid this? Or please suggest a better method to achieve similar functionality?

Best Answer

sajeesh - try using guidata rather than guihandles when trying to get the handles structure

 function drag_n_drop(fig_handle, eventdata)
 handles = guidata(fig_handle);
 % etc.

Not all handles can be returned using guihandles (see documentation for why).

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MATLAB: Image pixel info on

Hi Nirit, you can use the WindwoButtonMotionFunction of the Figure, your image 1 is in. Here is a quick example:

function m_easy_mouse_handling_example()
%example data
a = [1,1,1;2,2,2;3,3,3];
b = [10,12,14;16,18,20; 22 24 26];
%show the two figures
h_fig1 = figure()
h_ax1 = axes('Parent',h_fig1);
h_im1 = imagesc(a,'Parent',h_ax1);
h_fig2 = figure()
h_ax2 = axes('Parent',h_fig2);
h_im2 = imagesc(b,'Parent',h_ax2);
%set function which is used when mouse is over figure 1 (h_fig1)
set(h_fig1,'WindowButtonMotionFcn', @MouseMoveFcn)
function MouseMoveFcn(varargin)
    try
     mouse_pos = get(h_ax1, 'CurrentPoint');
     ii = round(mouse_pos(1,1));
     jj = round(mouse_pos(1,2));
       %show value of image 2 in command line
       disp(num2str(b(jj,ii)))  %please check, if order of dimensions is correct
      catch
          %catch error, if you are outside the image (to do)
      end
  end

MATLAB: How to move a plotted line vertically with mouse in a GUI

Ruben - here is a quick and rough way to do what I think that you want. It makes several assumptions which are hopefully valid for what you are trying to do, namely that plot (or some equivalent) function is used to plot the data on the 2D axes - so we have access to the x and y data that makes up the graphic. I've used GUIDE to mock up a GUI - it has a single axes (named axes1) and a push button (named pushbutton1). The button is used to plot some data on the axes. Its callback is

 % --- Executes on button press in pushbutton1.
 function pushbutton1_Callback(hObject, eventdata, handles)
 % define an array of colours
 colours = {'b','r','g','k','m','y'};
 % is the plot handles field defined for the handles structure?
 if ~isfield(handles,'plotHandles');
    handles.plotHandles = [];
 end
 % determine the number of handles (a maximum of six are plotted)
 numHandles = mod(length(handles.plotHandles),6);
 % get the x and y data for the sine wave, offset by the number of handles
 x   = -2*pi:0.01:2*pi;
 y   = sin(x) + numHandles;
 % plot the data
 h   = plot(handles.axes1,x,y,colours{numHandles+1});
 % update the plot handles to the array of plot handles
 handles.plotHandles = [handles.plotHandles ; h];
 % save the data


 guidata(hObject,handles);

The above just plots up to six sine waves on the axes. The important part is the saving of the plot graphics handle to the handles structure. This will allow us to manipulate the data later on.

Now, in order to enable the user to move a graphic object on the axes, we are going to assign three callbacks to the GUI/figure. In the Opening function (myGuiName_OpeningFcn), add the following code

 set(hObject, ...
    'WindowButtonDownFcn',   @mouseDownCallback, ...
    'WindowButtonUpFcn',     @mouseUpCallback,   ...
    'WindowButtonMotionFcn', @mouseMotionCallback);

hObject is our GUI/figure, and we are going to create callbacks for the (mouse) button down, up and motion events.

Each callback (within our m-file) is then defined.

The purpose of the mouseDownCallback is to check to see if the mouse down event is within axes1 (as opposed to anywhere else within the GUI). If this is true, then given the position within axes1, find (using the Euclidean distance equation) which plot graphics is closest to this position. This information is then saved for the mouse motion callback.

 function mouseDownCallback(figHandle,varargin)
    % get the handles structure


    handles = guidata(figHandle);
    % get the position where the mouse button was pressed (not released)
    % within the GUI
    currentPoint = get(figHandle, 'CurrentPoint');
    x            = currentPoint(1,1);
    y            = currentPoint(1,2);
    % get the position of the axes within the GUI
    axesPos = get(handles.axes1,'Position');
    minx    = axesPos(1);
    miny    = axesPos(2);
    maxx    = minx + axesPos(3);
    maxy    = miny + axesPos(4);
    % is the mouse down event within the axes?
    if x>=minx && x<=maxx && y>=miny && y<=maxy 
        % do we have graphics objects?
        if isfield(handles,'plotHandles')
            % get the position of the mouse down event within the axes
            currentPoint = get(handles.axes1, 'CurrentPoint');
            x            = currentPoint(2,1);
            y            = currentPoint(2,2);
            % we are going to use the x and y data for each graphic object
            % and determine which one is closest to the mouse down event
            minDist      = Inf;
            minHndl      = 0;
           for k=1:length(handles.plotHandles)
               xData = get(handles.plotHandles(k),'XData');
               yData = get(handles.plotHandles(k),'YData');
               dist  = min((xData-x).^2+(yData-y).^2); 
               if dist<minDist
                   minHndl = handles.plotHandles(k);
                   minDist = dist;
               end
           end
           % if we have a graphics handle that is close to the mouse down
           % event/position, then save the data
           if minHndl~=0
               handles.mouseIsDown     = true;
               handles.movingPlotHndle = minHndl;
               handles.prevPoint       = [x y];
               guidata(figHandle,handles);
           end
        end
    end

The purpose of the mouseUpCallback is to just reset any fields that correspond to the moving of the graphic, indicating that we are finished with the move.

 function mouseUpCallback(figHandle,varargin)
    % get the handles structure
    handles = guidata(figHandle);
    if isfield(handles,'mouseIsDown')
        if handles.mouseIsDown
            % reset all moving graphic fields
            handles.mouseIsDown     = false;
            handles.movingPlotHndle = [];
            handles.prevPoint       = [];
            % save the data
            guidata(figHandle,handles);
        end
    end

Finally, the purpose of mouseMotionCallback is to move the graphic from the previous position to the current one.

 function mouseMotionCallback(figHandle,varargin)
    % get the handles structure
    handles = guidata(figHandle);
    if isfield(handles,'mouseIsDown')
        if handles.mouseIsDown
            currentPoint = get(handles.axes1, 'CurrentPoint');
            x            = currentPoint(2,1);
            y            = currentPoint(2,2);
            % compute the displacement from previous position to current
            xDiff = x - handles.prevPoint(1);
            yDiff = y - handles.prevPoint(2);
            % adjust this for the data corresponding to movingPlotHndle
            xData = get(handles.movingPlotHndle,'XData');
            yData = get(handles.movingPlotHndle,'YData');
            set(handles.movingPlotHndle,'YData',yData+yDiff,'XData',xData+xDiff);
            handles.prevPoint = [x y];
            % save the data
            guidata(figHandle,handles);
        end
    end

I've attached the code to this answer. Hope that it helps!

Best Answer

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