.img-circle {
    border-radius: 50%; // set radius in percents
}

.img-fluid {
    max-width: 100%;
    height: auto;
}

.img-cover {
    width: 100%;
    height: 100%;
    overflow: hidden;
    -o-object-fit: cover;
    object-fit: cover;
    -o-object-position: 50% 50%;
    object-position: 50% 50%;
}