* Fixed format, only for 4 channel images

* structs can't be encoded this way, they need to have one child array
per struct member.
* i.e. struct of arrays, rather than an array of structs.

* basic safety included
* only respecting the types we emit

Co-authored-by: Andrew Murray <3112309+radarhere@users.noreply.github.com>

Co-authored-by: Andrew Murray <3112309+radarhere@users.noreply.github.com>

Co-authored-by: Andrew Murray <3112309+radarhere@users.noreply.github.com>

Co-authored-by: Andrew Murray <3112309+radarhere@users.noreply.github.com>

Co-authored-by: Andrew Murray <3112309+radarhere@users.noreply.github.com>

Co-authored-by: Andrew Murray <3112309+radarhere@users.noreply.github.com>