JSFiddle - React, Tailwind, and code Playground

HTML

<script src="http://openlayers.org/en/v3.6.0/build/ol-debug.js"></script>
<div id="map" class="map"></div>

CSS

.map {
        height: 200px;
        width: 400px;
        border:solid orange 1px;
      }





.ol-mouse-position {
  top: 8px;
  right: 8px;
  position: absolute;
}

.ol-scale-line {
  background: #95b9e6;
  background: rgba(0,60,136,0.3);
  border-radius: 4px;
  bottom: 8px;
  left: 8px;
  padding: 2px;
  position: absolute;
}
.ol-scale-line-inner {
  border: 1px solid #eeeeee;
  border-top: none;
  color: #eeeeee;
  font-size: 10px;
  text-align: center;
  margin: 1px;
  will-change: contents, width;
}
.ol-overlay-container {
  will-change: left,right,top,bottom;
}

.ol-unsupported {
  display: none;
}
.ol-viewport .ol-unselectable {
  -webkit-touch-callout: none;
  -webkit-user-select: none;
  -khtml-user-select: none;
  -moz-user-select: none;
  -ms-user-select: none;
  user-select: none;
  -webkit-tap-highlight-color: rgba(0,0,0,0);
}

.ol-control {
  position: absolute;
  background-color: #eee;
  background-color: rgba(255,255,255,0.4);
  border-radius: 4px;
  padding: 2px;
}
.ol-control:hover {
  background-color: rgba(255,255,255,0.6);
}
.ol-zoom {
  top: .5em;
  left: .5em;
}
.ol-rotate {
  top: .5em;
  right: .5em;
  transition: opacity .25s linear, visibility 0s linear;
}
.ol-rotate.ol-hidden {
  opacity: 0;
  visibility: hidden;
  transition: opacity .25s linear, visibility 0s linear .25s;
}
.ol-zoom-extent {
  top: 4.643em;
  left: .5em;
}
.ol-full-screen {
  right: .5em;
  top: .5em;
}
@media print {
  .ol-control {
    display: none;
  }
}

.ol-control button {
  display: block;
  margin: 1px;
  padding: 0;
  color: white;
  font-size: 1.14em;
  font-weight: bold;
  text-decoration: none;
  text-align: center;
  height: 1.375em;
  width: 1.375em;
  line-height: .4em;
  background-color: #7b98bc;
  background-color: rgba(0,60,136,0.5);
  border: none;
  border-radius: 2px;
}
.ol-control button::-moz-focus-inner {
  border: none;
  padding: 0;
}
.ol-zoom-extent button {
  line-height: 1.4em;
}
.ol-compass {
  display: block;
  font-weight:...

JavaScript

// landscape map url
//var img = 'https://kriezz.files.wordpress.com/2009/05/earth_map_3200-x-1200-dual-monitor.jpg';
//var extent = [0, 0, 3200, 1200];

// portrait map url
var img = 'http://www.mapsofworld.com/united-kingdom/maps/united-kingdom-map.gif';
var extent = [0, 0,1000, 1393]; 

var projection = new ol.proj.Projection({
  code: 'image',
  units: 'pixels',
  extent: extent
});

        var imgW = extent[2];
        var imgH = extent[3];
        var boxW = document.getElementById('map').offsetWidth;
        var boxH = document.getElementById('map').offsetHeight;

        var xRes = imgW / boxW;
        var yRes = imgH / boxH;
        var maxRes = xRes < yRes ? yRes : xRes;

window.map = new ol.Map({
    controls: ol.control.defaults().extend([
    new ol.control.ZoomToExtent({
      extent:extent
    })
  ]),
  layers: [
    new ol.layer.Image({
      source: new ol.source.ImageStatic({
        url: img,
        projection: projection,
        imageExtent: extent
      })
    })
  ],
  target: 'map',
  view: new ol.View({
    projection: projection,
    center: ol.extent.getCenter(extent),
    zoom: 0,
    maxResolution:maxRes
  })
});

//set the resolution to that of the xAxis.
map.getView().setResolution(xRes);

console.log('xRes: ' + xRes + ', yRes: ' + yRes + ', maxRes:' + maxRes);