bootstrap image thumbnail rounded code example
Example 1: bootstrap 4 center image
/* used mx-auto d-block */
<img class="mx-auto d-block" src="https://www.w3schools.com/bootstrap4/paris.jpg" alt="https://www.w3schools.com/bootstrap4/paris.jpg"/>
Example 2: bootstrap image size
.top1 {
height:390px;
background-color:#FFFFFF;
margin-top:10px;
overflow: hidden;
}
.top1 img {
height:100%;
}