From George Tarantilils, add missing handling of alpha channel.
From George Tarantilils, add missing handling of alpha channel.


marchelbling/osg,openscenegraph/osg,tomasthoresen/osg,marchelbling/osg,openscenegraph/osg,scrawl/osg,jtorresfabra/osg,artoolkit/osg,artoolkit/osg,jtorresfabra/osg,tomasthoresen/osg,artoolkit/osg,artoolkit/osg,jtorresfabra/osg,scrawl/osg,openscenegraph/osg,scrawl/osg,jtorresfabra/osg,tomasthoresen/osg,marchelbling/osg,marchelbling/osg,scrawl/osg,tomasthoresen/osg,openscenegraph/osg