MATLAB: Imrect object – delete notification

imrectinteractive rectangles

After creating an 'imrect' interactive object, in the context menu there is a delete option. Is there a callback to register when the 'imrect' object is deleted.

What I have so far:

 im_rect = imrect(ax, draw_rect);
 rectId = addNewPositionCallback(im_rect, @(pos)positionUpdateCallback(pos));

So I have access to the position update callback id. But I don't see how can I register any notifiers for the delete event. There is a 'removeNewPositionCallback', but I don't know whether this callback will be triggered on a delete. I checked both 'imrect' and 'imroi' help sections.

Maybe an alternative would be to add a custom delete command to the context menu, with a callback. Has anyone tried that ?

Best Answer

Unfortunately imrect and its similar functions are rather arcaic and don't really conform to more modern Matlab graphics objects, but it does derive from 'handle' and the handle class includes the following event

ObjectBeingDestroyed

which you can listen to as e.g.

addlistener( im_rect , 'ObjectBeingDestroyed', @(src,evt) disp( 'Rectangle died' ) )

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drawassisted is a simple wrapper around the image.roi.AssistedFreehand object. The function drawassisted really only constructs the ROI object and calls the draw method on the object so the user can begin drawing immediately. The problem with using drawassisted is that you can't set up listeners for the ROI object until after the object has already been drawn. For most events this isn't an issue but, as you observed, you can't set up DrawingStarted and DrawingFinished because the draw interaction will occur before you get the chance.

My suggestion would be to use the formal interface images.roi.AssistedFreehand directly:

https://www.mathworks.com/help/images/ref/images.roi.assistedfreehand.html

Step 1: Construct the ROI object and parent it to the axes

I = imread('peppers.png');
imshow(I);
ax = gca;
drawroi = images.roi.AssistedFreehand('Parent',ax);

Step 2: Set up the listeners

addlistener(drawroi,'DrawingStarted',@(~,~) disp('Drawing Has Started'));
addlistener(drawroi,'DrawingFinished',@(~,~) disp('Drawing Has Finished'));

Step 3: Call draw method to begin interactively drawing the ROI

draw(drawroi);

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Thomas,

When setting up the listener, use

addlistener(ROI, 'ROIMoved', @app.allevents)

Then, when defining allevents, use

function allevents(app, src, event)
    ...
end

Best Answer

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MATLAB: DrawingFinished event No response

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