bootstrap thumbnail grid code example

Example 1: bootstrap Image thumbnails

In addition to our border-radius utilities, you can use 
.img-thumbnail to give an image a rounded 1px border appearance.

<img src="..." alt="..." class="img-thumbnail">

Example 2: bootstrap card change image

.card-img-top {
    width: 100%;
    height: 15vw;
    object-fit: cover;
}