image width and height in bootstrap 4 code example

Example 1: bootstrap image size

.food1 img {
    width:100%;
    height: 230px;
}

Example 2: bootstrap image size

.top1 {
    height:390px;
    background-color:#FFFFFF;
    margin-top:10px;
    overflow: hidden;
}

.top1 img {
    height:100%;
}