How to draw an circle on the image where i show it on app.Image using app designer

Question

jaeyoung gwak 2023-3-5

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https://ww2.mathworks.cn/matlabcentral/answers/1923315-how-to-draw-an-circle-on-the-image-where-i-show-it-on-app-image-using-app-designer

评论： jaeyoung gwak 2023-3-8

采纳的回答： Cameron

Here's the image I used

imshow(image,'Parent', app.Images)

to show it on app.Image

I got the coordinate by using

app.point = get(0,'PointerLocation')

And I'm trying to draw an circle on the image when i click the image.

Is there anyway i could draw a circle on the image?

Also, I can't use the app.UIAxes buttonclick callback after getting the image on the UIAxes.

Thanks for all

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Answer 1

Cameron 2023-3-5

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https://ww2.mathworks.cn/matlabcentral/answers/1923315-how-to-draw-an-circle-on-the-image-where-i-show-it-on-app-image-using-app-designer#answer_1185580

在 MATLAB Online 中打开

If you have the Image Processing Toolbox, you can use the function drawcircle().

imshow(imread('peacock.jpg'))
h = drawcircle('Color','k','FaceAlpha',0.4);

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Cameron 2023-3-6

在 MATLAB Online 中打开

Your question is essentially "Why doesn't the callback for UIAxesButtonDown work after I put the image in the UIAxes?" Try this first:

function ButtonPushed(app, event)
    app.UIAxes.PositionConstraint = "innerposition";
    imshow(imread('peacock.jpg'),...
        'Parent',app.UIAxes);
    app.UIAxes.Visible = 1;
end

You can probably see some white space behind the image where the axes was. Click that and your UIAxesButtonDown will work. I would use a workaround for that though.

function ButtonPushed(app, event)
    app.UIAxes.PositionConstraint = "innerposition";
    b = imshow(imread('peacock.jpg'),...
        'Parent',app.UIAxes);
end
function UIAxesButtonDown(app, event)
    function allevents(src,evt)
        disp(['Circle current radius is: ' mat2str(evt.CurrentRadius)]);
        disp(['Circle current center is: ' mat2str(evt.CurrentCenter)]);
    end
    
    h = drawcircle(app.UIAxes,...
        'Color','k',...
        'FaceAlpha',0.4);
    
    addlistener(h,'MovingROI',@allevents);
    addlistener(h,'ROIMoved',@allevents);
end
function UIFigureWindowButtonDown(app, event)
    x = app.UIFigure.CurrentPoint(1);
    y = app.UIFigure.CurrentPoint(2);
    pos = app.UIAxes.InnerPosition;
    if x > pos(1) && x < pos(1) + pos(3) &&...
            y > pos(2) && y < pos(2) + pos(4)
        UIAxesButtonDown(app, event)
    end
end

Cameron 2023-3-7

在 MATLAB Online 中打开

I found an easier workaround for you. The callback for the UIAxes is not passed to its children - in this case the image. So we would have to set the callback for the image to the callback for UIAxes. There are only two lines you would need to add for your code.

% Button pushed function: Button
function ButtonPushed(app, event)
    [filename,pathname] = uigetfile({'*.jpg;*.tif;*.png;*.gif'});
    image = strcat(pathname,filename);
    imshow(image,'Parent', app.UIAxes);
    img = app.UIAxes.Children(1);
    img.ButtonDownFcn = app.UIAxes.ButtonDownFcn;
end
% Button down function: UIAxes
function UIAxesButtonDown(app, event)
    function allevents(src,evt)
            disp(['Circle current radius is: ' mat2str(evt.CurrentRadius)]);
            disp(['Circle current center is: ' mat2str(evt.CurrentCenter)]);
    end
    h = drawcircle(app.UIAxes,...
            'Color','k',...
            'FaceAlpha',0.4);
        addlistener(h,'MovingROI',@allevents);
        addlistener(h,'ROIMoved',@allevents);
end

jaeyoung gwak 2023-3-8

在 MATLAB Online 中打开

Thank you.

Appreciate about your concern.

I recognize I have to click the image twice to draw a circle.

so I give a change to the code a little bit.

classdef CircleROI < matlab.apps.AppBase
    properties (Access = private)
        ro
end
    
    methods (Access = private)
        
        function roi = circle(app)
            drawcircle(app.UIAxes,...
        'Color','k',...
        'FaceAlpha',0.4);
            roi = app.ro;
        end
        end
        % Callbacks that handle component events
    methods (Access = private)
        % Button pushed function: Button
        function ButtonPushed(app, event)
            app.UIAxes.PositionConstraint = "innerposition";
            imshow(imread('peacock.jpg'),'Parent',app.UIAxes);
            img = app.UIAxes.Children(1);
%             img.ButtonDownFcn = app.UIAxes.ButtonDownFcn;
img.ButtonDownFcn =   app.circle;
        end

But the problem is that I could only get the circle point once even if I click many times.

I draw some image to represent what i want to do.

Sorry for inconvenient and thank you for your help!!

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How to draw an circle on the image where i show it on app.Image using app designer

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How to draw an circle on the image where i show it on app.Image using app designer

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