How to change background color of an image in a GUI

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);

Answer 1

[Cris LaPierre]

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

of

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

[Cris LaPierre]

This post is also insightful on transparency and jpg images.

[Rocco Didio]

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]

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]

Thanks!