【Bootsrap4】圖片相關Class（img-fluid、img-thumbnail、rounded、float-left、mx-autio、d-block、text-center）

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

.img-thumbnail {
  padding: 0.25rem;
  background-color: #fff;
  border: 1px solid #ddd;
  border-radius: 0.25rem;
  -webkit-transition: all 0.2s ease-in-out;
  -o-transition: all 0.2s ease-in-out;
  transition: all 0.2s ease-in-out;
  max-width: 100%;
  height: auto;
}
.rounded {
  border-radius: 0.25rem;
}
.float-left {
  float: left !important;
}

.float-right {
  float: right !important;
}

.float-none {
  float: none !important;
}

.mx-auto {
  margin-right: auto !important;
  margin-left: auto !important;
}

.d-none {
  display: none !important;
}

.d-inline {
  display: inline !important;
}

.d-inline-block {
  display: inline-block !important;
}

.d-block {
  display: block !important;
}

.d-table {
  display: table !important;
}

.d-table-cell {
  display: table-cell !important;
}

.d-flex {
  display: -webkit-box !important;
  display: -webkit-flex !important;
  display: -ms-flexbox !important;
  display: flex !important;
}

.d-inline-flex {
  display: -webkit-inline-box !important;
  display: -webkit-inline-flex !important;
  display: -ms-inline-flexbox !important;
  display: inline-flex !important;
}

.text-justify {
  text-align: justify !important;
}

.text-nowrap {
  white-space: nowrap !important;
}

.text-truncate {
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.text-left {
  text-align: left !important;
}

.text-right {
  text-align: right !important;
}

.text-center {
  text-align: center !important;
}

See the Pen NyXRmw by Jerry (@fenture) on CodePen.