Generated by SassMeister.com.

Image white border on hover.html

<div class="image">
  <img src="https://www.yatzer.com/sites/default/files/media/slideshow/f5_out_my_window_gail_albert_halaban_new_york_glasshousewithdog_yatzer.jpg" />
  <div class="caption">
    A nice caption for out image
    <br>
    <button class="btn">Action Item</button>
  </div>
</div>

SassMeister-input.scss

// ----
// Sass (v3.4.21)
// Compass (v1.0.3)
// ----

body {
  background-color: #ddd;
  font-family: helvetica;
}
.image {
  margin-top: 30px;
  width: 400px;
  position: relative;
  &:before {
      content: '';
      position: absolute;
      top: 0;
      left: 0;
      right: 0;
      bottom: 15px;
      z-index: 2;
      border: 1px solid #fff;
      border-bottom: none;
      pointer-events: none;
      opacity: 0;
      -moz-transform: scale(1,1);
      -ms-transform: scale(1,1);
      -webkit-transform: scale(1,1);
      transform: scale(1,1);
      -moz-transition: all 0.1s ease-in-out;
      -o-transition: all 0.1s ease-in-out;
      -webkit-transition: all 0.1s ease-in-out;
      transition: all 0.1s ease-in-out;
    }
    &:hover:before {
      opacity: 1;
      top: 10px;
      left: 10px;
      right: 10px;
    }
  img {
    max-width: 100%;
    position: relative;
    
  }
  .caption {
    width: 100%;
    background-color: #fff;
    display: block;
    margin-top: -3px;
    padding: 13px;
    box-sizing: border-box;
    .btn {
      border: 1px solid #ddd;
      background-color: #fff;
      padding: 5px 10px;
      margin-top: 15px;
    }
  }
}

SassMeister-output.css

body {
  background-color: #ddd;
  font-family: helvetica;
}

.image {
  margin-top: 30px;
  width: 400px;
  position: relative;
}
.image:before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 15px;
  z-index: 2;
  border: 1px solid #fff;
  border-bottom: none;
  pointer-events: none;
  opacity: 0;
  -moz-transform: scale(1, 1);
  -ms-transform: scale(1, 1);
  -webkit-transform: scale(1, 1);
  transform: scale(1, 1);
  -moz-transition: all 0.1s ease-in-out;
  -o-transition: all 0.1s ease-in-out;
  -webkit-transition: all 0.1s ease-in-out;
  transition: all 0.1s ease-in-out;
}
.image:hover:before {
  opacity: 1;
  top: 10px;
  left: 10px;
  right: 10px;
}
.image img {
  max-width: 100%;
  position: relative;
}
.image .caption {
  width: 100%;
  background-color: #fff;
  display: block;
  margin-top: -3px;
  padding: 13px;
  box-sizing: border-box;
}
.image .caption .btn {
  border: 1px solid #ddd;
  background-color: #fff;
  padding: 5px 10px;
  margin-top: 15px;
}

SassMeister-rendered.html

<div class="image">
  <img src="https://www.yatzer.com/sites/default/files/media/slideshow/f5_out_my_window_gail_albert_halaban_new_york_glasshousewithdog_yatzer.jpg" />
  <div class="caption">
    A nice caption for out image
    <br>
    <button class="btn">Action Item</button>
  </div>
</div>