Stretch and scale a CSS image in the background - with CSS only

Question

I want that my background image stretch and scale depending on the browser viewport size.

I\'ve seen some questions on Stack Overflow that do the job, like

Answer 1

I wanted to center and scale a background image, without stretching it to the entire page, and I wanted the aspect ratio to be maintained. This worked for me, thanks to the variations suggested in other answers:

INLINE IMAGE: ------------------------

CSS ----------------------------------

html {
    height:100%;
}

#background {
    text-align: center;
    width: 100%; 
    height: 100%; 
    position: fixed;
    left: 0px; 
    top: 0px; 
    z-index: -1;
}

.stretch {
    margin: auto;
    height:100%;
}