How can i remove the crop mark in gui?

Hi, i have a crop button in the GUI, and i can click the button and then to crop the image displayed in axes. How do i remove the crop mark if i want to recrop again? I want to clear the crop mark if there is any in the image once i click the button.

function BtnCrop_Callback(hObject, eventdata, handles)
handles.output = hObject;
handles.currentAxes = get(handles.Axes,'Children');
if isempty(handles.currentAxes) == false
    promptMesg = sprintf('Are you sure to crop the image?');
    button = questdlg(promptMesg, 'Crop the image','Yes','No','Yes');
    if strcmpi(button,'Yes')
        handles.k = waitforbuttonpress;
        point1 = get(gca,'CurrentPoint');   
        handles.finalRect = rbbox;                   
        point2 = get(gca,'CurrentPoint');   
        point1 = point1(1,1:2);             
        point2 = point2(1,1:2);
        p1 = min(point1,point2);           
        offset = abs(point1-point2);         
        handles.x = round([p1(1) p1(1)+offset(1) p1(1)+offset(1) p1(1) p1(1)]);
        handles.y = round([p1(2) p1(2) p1(2)+offset(2) p1(2)+offset(2) p1(2)]);
        handles.cropSuccess = true;
        hold on
        axis manual 
        plot(handles.x,handles.y) ;
%         pause(2)
%         delete(hPlot);
    else
        handles.cropSuccess = false;
    end
else
    errordlg('No image is selected!');
end
guidata(hObject,handles);

The delete(hPlot) i tried is not exactly what i want. What i want is every time i click the button, it will check is there any crop mark in the image, if there is, then it will be removed (handles.x and hanles.y will also be deleted); if not, then i can start the new cropping.

Thanks a lot.

Answer 1

[Geoff Hayes]

You almost have it - you just need to assign the handle of the crop area to the handles object and then store this updated (handles) application data so that it will be there the next time the user presses the button.

If the user has pressed the Crop button, chosen Yes, and selected an area within the image then the code

 plot(handles.x,handles.y);

becomes

 % save the handle to the rectangle that surrounds the area of the image 
 % that is to be cropped
 handles.hCropRect = plot(handles.x,handles.y);

 % store the updated app data
 guidata(hObject,handles);

So we have a handle for the rectangle of the area to be cropped. You want this rectangle to be removed whenever the user presses the Crop button again, so we can do the following as the first line in the button callback (right before your above if statement, or as the first line within the if block)

 % check to see if the handles object has the hCropRect field
 if isfield(handles,'hCropRect');
     % delete only if not empty
     if ~isempty(handles.hCropRect)
         delete(handles.hCropRect);

         % clear the handle to denote that it has been deleted
         handles.hCropRect = [];

         % clear x and y
         handles.x = [];
         handles.y = [];

         % store the updated app data
         guidata(hObject,handles);
     end
 end

Try the above and see what happens!

I noticed that your code didn't have the guidata(hObject,handles) command - how were you able to access the handles.x, handles.y, and handles.finalRect outside of this function?

[Elsie]

oh, i put part of the code block, have updated it! Thanks a lot. i am trying it now!

[Image Analyst]

You will note, after running that code, that the image in the axes does not change. It will not get cropped.

[Elsie]

Hi, Geoff Hayes! it works perfectly! Thank you so much!

Answer 2

[Image Analyst]

I don't see any cropping going on. No indexing, no calling imcrop(), nothing. Using hPlot to get the handle to the line you plotted, and then deleting that handle will remove the line that you just drew from the image. It will not remove the x and y fields from handles like you said. The x and y fields will still be there, though the box in the overlay is gone.

You should probably put the delete(hPlot) before the call to plot:

if exist('hPlot', 'var')
  delete(hPlot);
end
hPlot = plot(handles.x, handles.y)
croppedImage = imcrop(originalImage, handles.finalRect);

[Elsie]

Hi, Image Analyst! i just put up the whole block code for this button function. i don't use imcrop() but the code above can perform cropping. I want to remove not only the line but also x, and y filed. eg. i didn't crop properly, and try to re-crop again, the data of x, and y need to be updated.

[Image Analyst]

Explain how. You're just defining a box but nothing gets cropped . No image gets cropped, no matrix gets cropped, at least not in the code you showed.