From Diane Delallée & Sukender, "Added some support of non-modulus-4 dimensions in S3TC-DXTC images (previous implementation seem just not to handle these properly).
- Added missing packing value on S3TC images. Images are coded with 4x4 blocs, whatever the image size. So there is an horizontal packing of 4 pixels (2 bytes in DXT1, 4 bytes in DXT2-5).
- Added crash guard against writing corrupted S3TC images.
Notes:
- What is missing is a support of "lines packing" in osg::Image (see code comments).
- S3TC-DXTC vertical flipping crashes (access violation) with some unusual dimensions (see code). I could not implement missing cases, so I added guards to avoid crashing."