How to change background color of an image in a GUI

Asked by Rocco Didio on 11 Sep 2019

Latest activity Commented on by Rocco Didio on 12 Sep 2019

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I want to insert an image (an arrow) on a button. I created the arrow in PowerPoint without background and then I saved that as image file. When I upload the image on the button it creates a white background. Can I substitute the white pixels with grey ([0.8 0.8 0.8]) pixels?

That's the code I use to upload the image

[a,map]=imread('arrow.jpg');

[r,c,d]=size(a);

x=ceil(r/100);

y=ceil(c/100);

g=a(1:x:end,1:y:end,:);

g(g==255)=5.5*255;

set(handles.btn,'CData',g);

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Products

MATLAB

Release

R2018a

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Answer by Cris LaPierre on 11 Sep 2019

Accepted Answer

If you can save your image as a png instead, see this post about displaying png images with transparent backgrounds.

Even with a png, images get displayed in an axes. Even if the image doesn't have a background, it will at least originally display in an axes with a background color set to white. You can turn that off using

axis off

set(gca,'Color','none')

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Rocco Didio on 12 Sep 2019

Thank you! I did this, but it still has a black backgroung

[A,map,transparency] = imread('arrow.png');
 image(A,'AlphaData',transparency);
 imshow(A,map,'Parent',handles.fig)
 axis off
 set(gca,'Color','none')

Cris LaPierre on 12 Sep 2019

You are doing image and imshow. Both display an image, but imshow does not accept the transparency settings. Can you make this work with just image(A,'AlphaData',transparency);

Rocco Didio on 12 Sep 2019

Thanks!

Products

MATLAB

Release

R2018a

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