Use alpha transparency to overlay images in App designer

Hi all,

I'm creating an app using app designer with Matlab R2022a. I have an axis (app.axisimage) and two images (app.im and GT_RGB).

I am trying to overlay both images in the axis, giving some transparency to the one on top (I guess the second one displayed). The transparency is controlled with the value of a slider (app.TransparencySlider).

I have tried several methods but non of them work.

My last tried piece of code si this:

imshow(app.im,'Parent',app.axisimage);
hold(app.axisimage,'on')
him = imshow(GT_RGB,'Parent',app.axisimage);
him.AlphaData = app.TransparencySlider.Value;
hold(app.axisimage,'off')

This shows the second image (GT_RGB) with the desired transparency, but the first image is not under it. Just in case it is important, both images are in single format with values ranging from 0 to 1.

Any clue of how could I do that? Thanks in advance for your help.

[Miguel Ángel]

As an update. I've seen the 'NexPlot property of the axes so I have also tried the following but it also does not work:

cla(app.axisimage)
app.axisimage.NextPlot = 'Add';
imshow(app.im,'Parent',app.axisimage);
him = imshow(GT_RGB,'Parent',app.axisimage);
him.AlphaData = app.TransparencySlider.Value;
app.axisimage.NextPlot = 'Replace';

Thanks!

Answer 1

[Miguel Ángel]

I finally solved it myself like this:

imshow(app.im,'Parent',app.axisimage);
app.axisimage.NextPlot = 'Add';
him = imshow(GT_RGB,'Parent',app.axisimage);
him.AlphaData = app.TransparencySlider.Value;
app.axisimage.NextPlot = 'Replace';

No need to cla(app.axisimage)

Thanks!