html {
    width: 100%;
    height: 100%;
}

body {
    width: 100%;
    height: 100%;
    position: relative;
}

img {
    position: absolute;
    top: 0;
    bottom: 0;
    left: 0;
    right: 0;
    margin: auto;
    width: 450px;
    height: 450px;
}