Update wmts-hidpi, add nicer-api-docs

nicer-api-docs/examples/export-map.js

@@ -0,0 +1,30 @@
+var map = new ol.Map({
+  layers: [
+    new ol.layer.Tile({
+      source: new ol.source.OSM()
+    })
+  ],
+  target: 'map',
+  view: new ol.View2D({
+    center: [0, 0],
+    zoom: 2
+  })
+});
+
+var exportPNGElement = document.getElementById('export-png');
+
+if ('download' in exportPNGElement) {
+  exportPNGElement.addEventListener('click', function(e) {
+    map.once('postcompose', function(event) {
+      var canvas = event.context.canvas;
+      exportPNGElement.href = canvas.toDataURL('image/png');
+    });
+    map.render();
+  }, false);
+} else {
+  var info = document.getElementById('no-download');
+  /**
+   * display error message
+   */
+  info.style.display = '';
+}