Edit in JSFiddle

<div class="separator" style="clear: both; text-align: center;">
  <a href="https://4.bp.blogspot.com/-Zo7aZr3kjbI/V1Zc2Y4BC7I/AAAAAAAAm1Y/vJpFypp5PpgoeQAIeFnCO4wGdhtAdgaMQCLcB/s1600/unnamed.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;">
  <img border="0" height="92" src="https://4.bp.blogspot.com/-Zo7aZr3kjbI/V1Zc2Y4BC7I/AAAAAAAAm1Y/vJpFypp5PpgoeQAIeFnCO4wGdhtAdgaMQCLcB/s200/unnamed.png" width="200" />
  </a>
</div>
<br />
<div class="separator" style="clear: both; text-align: center;">
  <a href="https://4.bp.blogspot.com/-Zo7aZr3kjbI/V1Zc2Y4BC7I/AAAAAAAAm1Y/vJpFypp5PpgoeQAIeFnCO4wGdhtAdgaMQCLcB/s1600/unnamed.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;">
  <img border="0" height="150" src="https://4.bp.blogspot.com/-Zo7aZr3kjbI/V1Zc2Y4BC7I/AAAAAAAAm1Y/vJpFypp5PpgoeQAIeFnCO4wGdhtAdgaMQCLcB/s320/unnamed.png" width="320" />
  </a>
</div>
<br />
<div class="separator" style="clear: both; text-align: center;">
  <a href="https://4.bp.blogspot.com/-Zo7aZr3kjbI/V1Zc2Y4BC7I/AAAAAAAAm1Y/vJpFypp5PpgoeQAIeFnCO4wGdhtAdgaMQCLcB/s1600/unnamed.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;">
  <img border="0" height="187" src="https://4.bp.blogspot.com/-Zo7aZr3kjbI/V1Zc2Y4BC7I/AAAAAAAAm1Y/vJpFypp5PpgoeQAIeFnCO4wGdhtAdgaMQCLcB/s400/unnamed.png" width="400" />
  </a>
</div>
<br />
<div class="separator" style="clear: both; text-align: center;">
  <a href="https://4.bp.blogspot.com/-Zo7aZr3kjbI/V1Zc2Y4BC7I/AAAAAAAAm1Y/vJpFypp5PpgoeQAIeFnCO4wGdhtAdgaMQCLcB/s1600/unnamed.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;">
  <img border="0" height="294" src="https://4.bp.blogspot.com/-Zo7aZr3kjbI/V1Zc2Y4BC7I/AAAAAAAAm1Y/vJpFypp5PpgoeQAIeFnCO4wGdhtAdgaMQCLcB/s640/unnamed.png" width="640" />
  </a>
</div>
<br />
<div class="separator" style="clear: both; text-align: center;">
  <a href="https://4.bp.blogspot.com/-Zo7aZr3kjbI/V1Zc2Y4BC7I/AAAAAAAAm1Y/vJpFypp5PpgoeQAIeFnCO4wGdhtAdgaMQCLcB/s1600/unnamed.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;">
  <img border="0" src="https://4.bp.blogspot.com/-Zo7aZr3kjbI/V1Zc2Y4BC7I/AAAAAAAAm1Y/vJpFypp5PpgoeQAIeFnCO4wGdhtAdgaMQCLcB/s1600/unnamed.png" />
  </a>
</div>
<br />
<div class="separator" style="clear: both; text-align: center;">
  <img border="0" src="https://4.bp.blogspot.com/-Zo7aZr3kjbI/V1Zc2Y4BC7I/AAAAAAAAm1Y/vJpFypp5PpgoeQAIeFnCO4wGdhtAdgaMQCLcB/s1600/unnamed.png" /></div>
<br />
<div class="separator" style="clear: both; text-align: center;">
  <img border="0" height="150" src="https://4.bp.blogspot.com/-Zo7aZr3kjbI/V1Zc2Y4BC7I/AAAAAAAAm1Y/vJpFypp5PpgoeQAIeFnCO4wGdhtAdgaMQCLcB/s320/unnamed.png" width="320" /></div>
<br />

img {
  width: 100%;
  height: auto;
}

.new {
  width: 100%!important;
}

.separator {
  width: 50%;
  position: relative;
  transition: all 100ms ease-in-out;
  cursor: pointer;
}

.separator:before {
  content: "\f00e";
  font-family: FontAwesome;
  position: absolute;
  bottom: 4px;
  right: 0;
  font-size: 2em;
  background: rgba(255, 255, 255, .6);
  padding: 10px;
  color: #444;
}

.separator.new:before {
  content: "\f010";
  font-family: FontAwesome;
  position: absolute;
  bottom: 4px;
  right: 0;
  font-size: 2em;
  background: rgba(255, 255, 255, .6);
  padding: 10px;
  color: #444;
}

$(".separator a > img").unwrap();

$('.separator').each(function() {
  $(this).click(function() {
    $(this).toggleClass('new');
  });
});

function resizeThumbsmall(size) {
  var image = document.querySelectorAll('.separator img');
  for (var i = 0; i < image.length; i++) {
    image[i].src = image[i].src.replace(/\/s200/, "/s" + size + "");
    image[i].width = size;
    image[i].height = size;
  }
}
resizeThumbsmall('1600');

function resizeThumbmedium(size) {
  var image = document.querySelectorAll('.separator img');
  for (var i = 0; i < image.length; i++) {
    image[i].src = image[i].src.replace(/\/s320/, "/s" + size + "");
    image[i].width = size;
    image[i].height = size;
  }
}
resizeThumbmedium('1600');

function resizeThumblarge(size) {
  var image = document.querySelectorAll('.separator img');
  for (var i = 0; i < image.length; i++) {
    image[i].src = image[i].src.replace(/\/s400/, "/s" + size + "");
    image[i].width = size;
    image[i].height = size;
  }
}
resizeThumblarge('1600');

function resizeThumbextralarge(size) {
  var image = document.querySelectorAll('.separator img');
  for (var i = 0; i < image.length; i++) {
    image[i].src = image[i].src.replace(/\/s640/, "/s" + size + "");
    image[i].width = size;
    image[i].height = size;
  }
}
resizeThumbextralarge('1600');