Google Maps: How to add shadow to custom marker?

I'm using the new functionality of Animation (bouncing) found in Google Maps JavaScript API v3.

http://code.google.com/apis/maps/documentation/javascript/overlays.html#MarkerAnimations

In the examples in the linked code above, the default map marker icons have a dropshadow show on the map during the开发者_Python百科 bounce.

I'm using a custom map marker icon that is a PNG.

Question: How do I create a dropshadow for my custom map marker icon that will also be shown when doing the Animation (bounce) effect?

UPDATE

Here is an example using the default map marker icon.

http://code.google.com/apis/maps/documentation/javascript/examples/marker-animations-iteration.html

How do I do this using a custom map marker icon that also has a drop shadow.

Got it to work.

http://jsfiddle.net/brWhw/

you can use some kind of a shadow maker online, like:

http://www.cycloloco.com/shadowmaker/shadowmaker.htm