Presto layered graphics

Hi,

I’m using the Pico Graphics library to draw a combination of bitmaps and text. Is there a way to clear a layer to be transparent, or to use a transparent brush?

What I’d like to do is draw a bitmap to layer 0 which is relatively static and use layer 1 for more dynamic overlays. And to avoid having to redraw layer 0 just because something in layer 1 changes. I would then just clear the regions of layer 1 that have changed and then draw the new content.

Thanks!