Using impixelinfo with appDesigner

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Roger Breton
Roger Breton on 27 Dec 2021
Answered: Rishabh Singh on 12 Jan 2022
I am running into the following error with appDesigner, when trying to retrieve the pixel info an an image component :
This is the app interface :
All I want to achieve, at this stage, is to get some information about the pixels at the mouse position.
I thought of using impixelinfo but it needs some argument? I tried :
But that's when I get the above error message. I read somewhere that impixelinfo does not work with appDesigner?
Eventually, I would like to capture the mouseover and mouseclick events so that I can display not only the image RGB values but also, and more importantly, the CIE Lab values. Ultimately, I would like to turn mouseclicks into a selected 3D points in the scatter3 plot on th right... Tall order for a Matlab and appDesigner newbie like me -- I know.
Any help is appreciated.
  1 Comment
Roger Breton
Roger Breton on 29 Dec 2021
Just want to say that I'm studying the code here :
There is a LOT I have to learn but, withe help of the debugger, it helps a lot.
So far, I ran the code at the above link and I can see that this partly does what I need to do, which is to return some values in response to a mouseover movement over some graphic object. To wrap one's brain around the used symbols is not for the faint of heart... Needless to say, I'm discovering a whole world but I'm not totally lost, programming wise. I just have not a "mental" map of Matlab's object model... But I'm getting there.

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Answers (1)

Rishabh Singh
Rishabh Singh on 12 Jan 2022
A possible workaround for your problem could be using a figure window outside your app.
function ButtonPushed(app, event)
img =;
hp = impixelinfo();
set(hp, 'Position', [5 1 300 20]);
Here I have used a "ButtonPushed" callback to trigger the figure window, and there you can use "impixelinfo". You can also explore "datacursormode" and "getCursorInfo" for picking up data points using cursor.
Hope this helps.


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