JPEG compression in wkw

[normanrz]

I noticed that catmaid and neuroglancer support jpeg compression for their file formats. I was wondering if it made sense to also support jpeg compression on a per-bucket basis in wkw. That would be an option to gain higher ratios through lossy, but still usable compression.

Any thoughts @amotta @philippotto?

[normanrz]

Relates to #23

[philippotto]

Also see #23 where @amotta already outlined a few thoughts.

From my point of view, this should definitely be worth a try. At the moment, cubes are compressed per bucket. We already have the option for LZ4 vs. LZ4HC. So, adding other compression algorithms should be relatively easy, if I'm not missing anything?

Regarding "lossy": The different magnifications could be viewed as lossy compressions, as well (very lossy :)). So, why not adding lossy image compression algorithms? We could even think about having mag 1 in original quality and lossy quality. Then, the lossy version could be used for flight-mode and the other version for ortho (would need support in WK and not wkw, but just as a general idea...)

[amotta]

Hej hej

As you can see from issue #23, I'm all in favor of adding (potentially lossy) compression for image data. So, feel free to go ahead and implement this.

Personally, I don't know enough about volumetric image compression to argue for / against any particular algorithms. But I did find out that the OpenJPEG library contains an implementation of the JP3D.