Reset globalAlpha back to its initial after mutating it for drawing layers

examples/export-map.js

@@ -98,6 +98,7 @@ document.getElementById('export-png').addEventListener('click', function () {
         }
       }
     );
+    mapContext.globalAlpha = 1;
     if (navigator.msSaveBlob) {
       // link download attribute does not work on MS browsers
       navigator.msSaveBlob(mapCanvas.msToBlob(), 'map.png');

examples/export-pdf.js

@@ -83,6 +83,7 @@ exportButton.addEventListener(
           }
         }
       );
+      mapContext.globalAlpha = 1;
       const pdf = new jspdf.jsPDF('landscape', undefined, format);
       pdf.addImage(
         mapCanvas.toDataURL('image/jpeg'),