Adding mapbox-gl branch

mapbox-gl/examples/export-map.js

@@ -0,0 +1,41 @@
+var map = new ol.Map({
+  layers: [
+    new ol.layer.Tile({
+      source: new ol.source.OSM()
+    }),
+    new ol.layer.Vector({
+      source: new ol.source.GeoJSON({
+        projection: 'EPSG:3857',
+        url: 'data/geojson/countries.geojson'
+      })
+    })
+  ],
+  target: 'map',
+  controls: ol.control.defaults({
+    attributionOptions: /** @type {olx.control.AttributionOptions} */ ({
+      collapsible: false
+    })
+  }),
+  view: new ol.View({
+    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.renderSync();
+  }, false);
+} else {
+  var info = document.getElementById('no-download');
+  /**
+   * display error message
+   */
+  info.style.display = '';
+}