add accessors for tilepart division

[bradh]

This exposes the current tilepart division setting. This avoids needing a shadow variable in the libheif plugin.

Also fixes a couple of typos in the applicable enumeration. I can split that out as a separate PR if preferred.

[aous72]

Hi Brad,

This is all reasonable.

However, it is worth saying that when a tile bitstream is partitioned into multiple tile-parts, the only requirement is that each tile part contains complete precinct bitstreams; that is, a precinct bitstream cannot be broken across two tile parts.

While OpenJPH can create tile parts in a couple of specific ways (resolution, component), as you have noticed, other tools may partition the bitstream in other ways. Would that be a problem for libheif?

Cheers,
Aous.

[bradh]

While OpenJPH can create tile parts in a couple of specific ways (resolution, component), as you have noticed, other tools may partition the bitstream in other ways. Would that be a problem for libheif?

This is only on the libheif encoder side (i.e. setting it as an option parameter, and reading that parameter back), so I am confident it won't be a problem at this stage.

Decoding is handled separately - its a whole different plugin.