Icon inside button

Hello, icon iside the button dosn't change its size.
My code is:

FileResource right = new FileResource(new File("right.png"));
Image upT = new Image();
upT.setIcon(right);
upT.setWidth("100%");
upT.setHeight("100%")

Button takes all possible place in layout, but icon is bigger than button size.
What should I do to make Icon resize, accordingly button size&

Have you tried to set the image size with CSS? 

Kind regards,
Felype