.overlay {
    position: absolute;
    top: 0; bottom: 0; left: 0; right: 0;
    opacity: 0;
    transition: all .15s ease-in-out;
}
.overlay:hover {
    background: linear-gradient(to bottom, rgba(0,0,0,0) 50%, rgba(0,0,0,0.7));
    opacity: 1;
}
.overlay .label {
    position: absolute;
    bottom: 0;
    margin: 0 0 1.3em 1em;
    color: #eee;
    font-size: 1em;
    opacity: 0;
}
.overlay:hover .label {
    opacity: 1;
}

#image_preview {
    width: 100%;
    height: 100%;
    object-fit: contain;
}