In 1.5, new API was added to allow for the creation of non-opaque
VolatileImages:
   GraphicsConfiguration.createVolatileImage(int w, int h, int trans);

The OpenGL-based Java 2D pipeline currently returns a system memory based
VolatileImage from this method (if the trans parameter is not OPAQUE). In
theory, we could create a pbuffer in this case, if the GraphicsConfig supports
a stored alpha channel. That would allow for hardware accelerated rendering
to a translucent offscreen surface, and copies from that surface would also
be accelerated.

A number of developers, especially on javagaming.org, are looking forward to
using translucent VolatileImages, so we should do what we can to support this
feature in hardware.