How can I use the multiply blend mode on a canvas in real time?
===

Essentially, I have two canvases (one is an invisible canvas used for drawing) and I want to blend the invisible canvas onto the visible one with the multiply blend mode.  Context.globalCompositeOperation does not include multiply (though it should, in my opinion) and using imageData to manually blend the canvases is too slow (I need to be able to do this at 60fps).  Is there any faster method I could use to blend the canvases?  I believe this could be done using WebGL, but I have no experience using it.