Stack two images and merge them into a single one in javascript

I've made some research on this but haven't found any solution, so I'm not sure it is even possible, but here is my problem:

I'm developing a website using only HTML/CSS + Javascript, using a REST API, and I need to merge two images in one to use it as an icon for the google maps API. I can't do it on the server because it depends o开发者_如何学JAVAn the client, and I need to provide an image at the end. I've seen some things, like pixastic, but it isn't supported in IE and unfortunately some people still use that :p...

Do you know other ways to do that?

Thanks in advance!

EDIT: actually, you just have to use Google's overlay tools in the API. I just put one Marker on top of the other and adjusted the size and position using the MarkerImage class.

You could just put one over the other and change the opacity of the top one: http://jsfiddle.net/cAWJs/

Using blend modes like your example site you would need canvas support though.