pymicro tutorial: compressing X-ray tomography volumes with multiple semantic segmentations (voxel-wise categorical values)

These are mock volumes for a tutorial in pymicro: https://github.com/heprom/pymicro

See the tutorial with the same name in the package's repository.

You can also see a similar demo .ipynb here: https://github.com/joaopcbertoldo/gfpa66-volumes

The files in `raws.zip` and `pa66_256.zip` are all from a 3D x-ray computed tomography (XCT) of a polyamide 66 reinforced by glass fibers.