Setting a KML layer transparency

Question

Is there a way to set the transparency of a kml layer when you add it? I am adding a kml layer that you cannot see through to the streets below. Is there a way to accomplish this

 var map = new google.maps.Map(document.getElementById('map-canvas'), mapOptions);

  var ctaLayer = new google.maps.KmlLayer({
    url: 'images/test3.kml'
  });

  var ctaLayer2 = new google.maps.KmlLayer({
    url: 'images/test.kml'
  });
  var ctaLayer3 = new google.maps.KmlLayer({
    url: 'images/kmztest2.kmz'
  });
  ctaLayer3.setMap(map);
  ctaLayer2.setMap(map);
  ctaLayer.setMap(map);
}

google.maps.event.addDomListener(window, 'load', initialize);

Answer 1

As KML are added by Google Maps API as images in the DOM, you can change its opacity with CSS by searching the <img> elements that contain "kml" in its src attribute:

#map img[src*='kml'] {
    opacity: .5;
}

Also, you can achieve this using jQuery:

jQuery("#map").find("img[src*='kml']").css("opacity","0.5");

But keep in mind that when user zoom's out or moves the map, new KML images will be loaded, so you'll have to call that jQuery function again.

Answer 2

You can't modify the opacity of the polygons in a KmlLayer. You have three options (that I can think of):

1. define the opacity in the KML

example, the KML looks like this:

<Style
  id="Style1">
  <LineStyle><color>66000001</color><width>1</width></LineStyle>
  <PolyStyle>
    <color>00ff6633</color>  <!-- first 00 is opacity of zero -->
    <fill>1</fill>
    <outline>1</outline>
  </PolyStyle>
</Style>
<Placemark id="Opacity0">
  <name>Opacity 0</name>
  <visibility>1</visibility><open>0</open><styleUrl>#Style1</styleUrl>
  <Polygon><extrude>0</extrude><tessellate>1</tessellate><altitudeMode>clampToGround</altitudeMode>
    <outerBoundaryIs><LinearRing><coordinates>-116.365673309192,43.6628960911185 -116.365591334179,43.6560111958534 -116.364375539124,43.6559975333512 -116.364402864128,43.6483204644173 -116.359539767727,43.6483955662698 -116.359567092732,43.64422573708 -116.356452545151,43.6442223004997 -116.356329582632,43.6403188481927 -116.355482675135,43.6384234484285 -116.354444492608,43.6376550793648 -116.354198567569,43.6375697515905 -116.354198567569,43.6375560890883 -116.354348855093,43.6375355534256 -116.352818906307,43.6375834140927 -116.349636046216,43.6375697515905 -116.349677033722,43.6339155770838 -116.317438473925,43.6339155770838 -116.314392238855,43.6339600011706 -116.314187301323,43.6484194546938 -116.334391040727,43.6484843306243 -116.33440470323,43.6627594660968 -116.335292598233,43.6629438679665 -116.336767980829,43.6629097536206 -116.359348576516,43.6629985179752 -116.360673587769,43.6628994438797 116.365673309192,43.6628960911185</coordinates>

 </LinearRing></outerBoundaryIs></Polygon>
 </Placemark>

2. import the KML into FusionTables, and use a FusionTablesLayer (which allows you to change the opacity of polygons) (No longer useful as FusionTables will be turned down/off on December 3, 2019)

3. If the KML is not too complex, use a third party parser (geoxml3 or geoxml-v3, which will parse the KML and render it as native Google Maps Javascript API v3 objects (which allow you to modify the opacity).

Answer 3

This solution is not perfect because it causes a slight flash when changing zoom levels, but some may find this useful:

google.maps.event.addListener(map, 'tilesloaded', function() {
            $("#map").find("img").css("opacity","0.5");
});