CSS - Transparent PNG centered in a DIV with responsive background

I have a DIV with a responsive background. I'm trying to place a centered png "logo" over the DIV (or the background, if you prefer). That's what I have:

.divWithBG {
    background-image: url(...);
    background-size: contain;
    background-repeat: no-repeat;
    width: 100%;
    height: 0;
    padding-top: 45.45%; /* (h/w) x 100 */
    margin-bottom: 30px;
}
.divWithBG img{
    display: block;
    margin: 0 auto;
}

¿What I need to do to place the image inside the div? Centered both, vertically and horizontally.

Many thanks in advance.

via Chebli Mohamed