How to get the current viewport of the map out of OpenLayers as geometry, bounding box or wkt?
For OpenLayers 2:
Map.getExtent()
...will return a Bounds, which you can then use to get the lat/long coordinates in any number of ways: http://dev.openlayers.org/apidocs/files/OpenLayers/BaseTypes/Bounds-js.html#OpenLayers.Bounds
Ideally, you'd turn the vectors into Geometry objects and check them against Map.getExtent() using Bounds.intersectBounds() to see if they're in the current viewport.
For OpenLayers 3:
ol.Map.getView().calculateExtent(map.getSize())
...will return an array of coordinates, representing the bounding box of the extent.
For openlayers 5.3.
olmap.getView().calculateExtent(olmap.getSize());
Runnable code for openlayers 5.3 follows:
(V6.5.0 has the same API document concerning the use of getView and getSize, the code above should also work with it.)
// import modules
const Map = ol.Map;
const View = ol.View;
const TileLayer = ol.layer.Tile;
const VectorLayer = ol.layer.Vector;
const fromLonLat = ol.proj.fromLonLat;
const OSM = ol.source.OSM;
const VectorSource = ol.source.Vector;
const Overlay = ol.Overlay;
const Style = ol.style.Style;
const Fill = ol.style.Fill;
const Text = ol.style.Text;
// basic base layer: raster
var rasterLayer = new TileLayer({
source: new OSM()
});
// create main map with a base map
var mapcenter = [100.5330981, 13.7364029];
var olmap = new Map({
layers: [rasterLayer] /* more layers can be added here, or later steps */ ,
target: document.getElementById("map1"),
view: new View({
center: fromLonLat(mapcenter),
zoom: 17
})
});
// add eng-chula marker
const engchula = [100.5330981, 13.7364029];
var marker1 = new Overlay({
position: fromLonLat(engchula),
positioning: "center-center",
element: document.getElementById("marker1"),
stopEvent: false
});
// 'Eng-chula' label
var engchula1 = new Overlay({
position: fromLonLat(engchula),
element: document.getElementById("engchula1")
});
// add overlay(s) to 'olmap'
olmap.addOverlay(marker1);
olmap.addOverlay(engchula1);
// Demo the use of .getSize()
var sizes = olmap.getSize(); //units:pixels; columns x rows
console.log("getSize (pixels): " + sizes); //2 numbers
// get `extent` through getView()
var extent = olmap.getView().calculateExtent(olmap.getSize());
console.log("Extent, LL_x: " + extent[0]); //left
console.log("Extent, LL_y: " + extent[1]); //bottom
console.log("Extent, UR_x: " + extent[2]); //right
console.log("Extent, UR_y: " + extent[3]); //top
/*
Status:ok
*/#map1 {
width: 70%;
height: 500px;
}
#marker1 {
width: 25px;
height: 25px;
border: 2px solid #088;
border-radius: 10px;
background-color: firebrick;
opacity: 0.75;
}<head>
<link rel="stylesheet" href="https://openlayers.org/en/v5.3.0/css/ol.css" type="text/css">
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/css/bootstrap.min.css">
<script src="https://cdn.rawgit.com/openlayers/openlayers.github.io/master/en/v5.3.0/build/ol.js"></script>
<script src="https://code.jquery.com/jquery-2.2.3.min.js"></script>
</head>
<body>
<H3>Openlayers v5.3.0 Web Map with Geojson Data</H3>
<div id="map1" class="map"></div>
<i>:</i>
<p id="p1">Find "<b>Eng_Chula</b>", then click it.</p>
<div style="display: none;">
<!-- Clickable label for Eng-Chula -->
<a class="overlay" id="engchula1" target="_blank" href="http://eng.chula.ac.th">Eng_Chula</a>
<div id="marker1" title="Marker1"></div>
</div>
</body>