gallery-frontend/src/app/gallery/display-image/display-image.component.css

.modal-container {
    position: fixed;
    top: 0;
    right: 0;
    bottom: 0;
    left: 0;
    background: rgba(0, 0, 0, 0.75);
    z-index: -1;
    opacity: 0;
    -webkit-transition: opacity 150ms ease-in;
    -moz-transition: opacity 150ms ease-in;
    transition: opacity 150ms ease-in;
}

.modal-container .image {
    display: flex;
    margin: auto;
    margin-top: 15px;
}