Control image transparency with a slider- appDesigner

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João Mendes
João Mendes 2019-7-15
编辑： Adam Danz 2021-2-10
Hi all,
I'm trying to control de tranparency of two images using a slider.
Currently, I don't know how to do the code for this feature with a callback function with the slider.
Can anybody help me?
What I wanted, for a better understanding, is that when I'm at a max value, I only see one of the images and at the min value I only see the other. Obviously, when I move the slider I want the transparency of them to change.
Thanks in advance
JM
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João Mendes
João Mendes 2019-7-15
First of all, thanks.
I'm a truly begginer and I didn't fully understand your point.
Could you please explain that to me with some code examples?
Sorry and thanks
Adam
Adam 2019-7-15
It would be easier if you post the relevant code you currently have. I don't really have time for long answers from scratch, hence me adding a comment rather than an 'Answer'

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Adam Danz
Adam Danz 2019-7-15
编辑：Adam Danz 2021-2-10
This should get you started.
Two images are plotted on top of each other. A slider is added that sets the AlphaData of the top image.
% Create a figure with two images overlayed
fig = uifigure('HandleVisibility','on');
[X,cmap] = imread('corn.tif');
imshow(X,cmap);
hold on
[X2,map] = imread('peppers.png');
img2 = imshow(X2,map);
% Create a GUI with a slider that controls the 'AlphaData' value of the currently selected object
sld = uislider(fig,'Position',[50,50,300,3],'Value',1,'Limits',[0,1],...
'ValueChangingFcn', @(sld,event)changeTransparencyFcn(sld,event,img2),...
'BusyAction', 'cancel');
% set the slider properties such as position etc....
% % https://www.mathworks.com/help/matlab/ref/uislider.html
function changeTransparencyFcn(~, event, hobj)
% hobj is the image object handle
set(hobj,'AlphaData', event.Value)
drawnow limitrate
end
Changes made to improve answer on Feb 9, 2021.
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Georg Edelmann
Georg Edelmann 2020-2-27
Hey thanks for your quick response!
How else could it be done?
function changeSensitivityFcn(sld, event)
Sensitivity=sld.Value
drawnow()
end
Using this code, i am able to change my Sensitivity Parameter as i can see in the Command Window, but the image itself does not change. Why?
Thanks
Adam Danz
Adam Danz 2020-2-27
In my answer,
set(gco,'AlphaData', sld.Value)
the slider is controlling the AlphaData property values of the currently selected image.
The link I provided in my previous comment lists properties of images. I don't know what you define as "sensitivity". If you can't figure that out, it might be better to post a new questions since I have limited time right now (feel free to link to this answer).

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