flex wrap image responsive

keep image placed in center and its proportion yet being responsive.

by tea4two

HTML

<div class="box">
  
  <div>
    <p class="thumb-box">
      <img src="http://via.placeholder.com/150x150/ddd/fff" alt="" class="post-thumbnail">
    </p>
    <p class="cap">1</p>
  </div>
  
    <div>
    <p class="thumb-box">
      <img src="http://via.placeholder.com/150x150/ddd/fff" alt="" class="post-thumbnail">
    </p>
    <p class="cap">2</p>
  </div>
  
    <div>
    <p class="thumb-box">
      <img src="http://via.placeholder.com/150x150/ddd/fff" alt="" class="post-thumbnail">
    </p>
    <p class="cap">3</p>
  </div>
  
    <div>
    <p class="thumb-box">
      <img src="http://via.placeholder.com/150x150/ddd/fff" alt="" class="post-thumbnail">
    </p>
    <p class="cap">4</p>
  </div>
  
    <div>
    <p class="thumb-box">
      <img src="http://via.placeholder.com/150x150/ddd/fff" alt="" class="post-thumbnail">
    </p>
    <p class="cap">5</p>
  </div>
  
    <div>
    <p class="thumb-box">
      <img src="http://via.placeholder.com/150x150/ddd/fff" alt="" class="post-thumbnail">
    </p>
    <p class="cap">6</p>
  </div>
  
      <div>
    <p class="thumb-box">
      <img src="http://via.placeholder.com/150x150/ddd/fff" alt="" class="post-thumbnail">
    </p>
    <p class="cap">7</p>
  </div>
</div>

SCSS

* {
  box-sizing: border-box;
}
.box {
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  height: 100vh;
  
  
  > div {
    width: 30%;
    height: 30%;
    border: 1px solid black;
  }
  .thumb-box { //画像サイズの基準となる
    height: 80%;
    display: flex;
    justify-content: center;
    align-items: center;
    background-color: yellow;
  }
  .post-thumbnail {
    max-width: 100%;
    max-height: 100%;
    display: block;
    margin: 0 auto;
  }
}