[osg-users] minor change: move assumeSizedInternallFormat from Texture to Image

[Robert Osfield]

 I am just heading offline for the evening so a quick update.  I have
rolled out the use of GLenum Texture::selectSizedInternalFormat(const
osg::Image* image) to the other glTexStorage cases in the OSG and also
when doing this spotted a bug in the allocation/reuse of GL texture
objects - to fix this issue I can to refactor the code to push the
generateAndAssignTextureObject(..) calls to after where the internal
format is finally decided upon:

https://github.com/openscenegraph/OpenSceneGraph/commit/d37b826a745b4638666b0d53c613033a17df4397

Could those who've see issue with OSG master have a look at master now
to see if it's working fine.

Cheers,
Robert.