Image 'CurrentPoint' properties does not exist? (appDesigner Image Component)

I found some code designed to retrieve an UIAxes component x,y coordinates when 'traversed' by the mouse :

pm.enterFcn = [];

pm.exitFcn = @(~,~) set(app.CurrentPositionEditField, 'Value', '');

pm.traverseFcn = @(~,~) set(app.CurrentPositionEditField, 'Value', sprintf('%.2f, %.2f', app.UIAxes.CurrentPoint(1,1:2)));

iptSetPointerBehavior(app.UIAxes, pm)

iptPointerManager(app.UIFigure,'enable');

set(app.UIFigure,'WindowButtonMotionFcn',@(~,~)NaN)

It works like a charm, except my application is not after 'charts' but 'images', RGB images. So I add an Image component to the interface and got this :

You see the image on the right? I would like to retrieve the mouse position when it hovers the image. And eventually use those coordinates to retrieve the image RGB pixel values.

So I tried to modify the above code, by changing the 'traverseFcn' and 'iptSetPointerBehavior' to use an Image component instead but, as it turns out, Image components don't have CurrentPoint properties?

I've been searching the Community, the internet and Matlab Help on how to do this to no avail.

Any help is appreciated.

[Rik]

As far as I can tell, uiaxes do have the current point property. Have you tried putting your callback in a separate function so you can do the indexing in a variable instead of the property?

Answer 1

[Roger Breton]

I diverged quite a bit... Matlab's graphics is hard to conceptualize. But I'm sloooowly getting there. I had to put appDesigner on the back burner and go back to simple script file, in order to make some progress in my humble project. Here's the code I finally got :

global img

img=imread('Bird.jpg');

h = imshow(img);

set (gcf, 'WindowButtonMotionFcn', @mouseMove);

function mouseMove (object, eventdata)

global img;

C = get (gca, 'CurrentPoint');

SmallX = num2str(C(1,1));

SmallY = num2str(C(1,2));

RGB = img(SmallX, SmallY, :)

title(gca, ['(X,Y) = (', SmallX, ', ',SmallY, ') RGB = ', num2str(RGB(1)), ', ', num2str(RGB(2)), ' ,', num2str(RGB(3))]);

end

I tried very hard to stick with impixelinfo(). I found a way to extract the RGB values returned in the 'string' but I still had to convert RGB to Lab with a cform. My current solution may not be every elegant but it does what I want. Next step is to enhance the mouseMove function with a call to applycform or sRGB2Lab to obtain the Lab values for the image pixels. At that point, I'll add them to the title and be done.

I'm not sure I'll be able to "port" this code to my appDesigner app? We'll see. Thank you for your interest. Hope this helps someone. I'm really a Matlab newbie...

[Rik]

For general advice and examples for how to create a GUI, have look at this thread.

Using a global variable is not required.

For the title I would suggest using sprintf to compose the text.