img {
    opacity: 1;
    transition: opacity .5s;
    -webkit-transition: opacity .5s;
  }
  img[data-src] {
    opacity: 0;
  }

.wrap_thumb{
  width: 100%;
  position: relative;
  height: 0;
  overflow: hidden;
  padding-bottom: 100%;
  background: #efefef;
}
.wrap_thumb50 {
  padding-bottom: 50%;
}
.wrap_thumb64 {
  padding-bottom: 64%;
}
.wrap_thumb138 {
  padding-bottom: 138%;
}
.wrap_thumb28 {
  padding-bottom: 28%;
}