.ui-widget-overlay {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: #aaa;
    opacity: .3;
}
.popupwindow-div {
}
    .popupwindow-div img {
        object-fit: contain;
        max-width: 100%;
        max-height: 100%;
        width: auto;
        height: auto;
    }